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Histidine
Kinds of Histidine Terms modified by Histidine Selected AbstractsBinding of Oxovanadium(IV) to Tripeptides Containing Histidine and Cysteine Residues and Its Biological Implication in the Transport of Vanadium and Insulin-Mimetic CompoundsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2005Eugenio Garribba Abstract The complexation of VIVO ion with three tripeptides of biological importance containing L -histidine or L -cysteine (HisGlyGly, GlyGlyHis and GlyGlyCys) has been studied. This study was performed in aqueous solution by the combined application of potentiometric and spectroscopic (electronic absorption and EPR) techniques. The results indicate that these oligopeptides, if a ligand-to-metal molar ratio of 10 or 15 is used, can keep VIVO ion in solution until the deprotonation of the amide group with the donor set (NH2, CO, Nimax) for HisGlyGly or (COO,, CO) for GlyGlyHis and GlyGlyCys. In all the systems, at pH values around neutrality, a VOLH,2 species is formed with an (NH2, N,, N,, COO,) donor set for HisGlyGly, (NH2, N,, N,, Nim) for GlyGlyHis and (NH2, N,,N,, S,) for GlyGlyCys. These species, and those with onedeprotonated amide group coordinated to the VIVO ion, can be detected by EPR spectroscopy. The N,(amide) contribution to the hyperfine coupling constant along the z axis, Az, depends on the total charge of the donor atoms in the equatorial plane. The participation of albumin in the transport of vanadium and insulin-mimetic VIVO compounds is reconsidered based on these results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Molecular Tailored Histidine-Based Complexing Surfactants: From Micelles to HydrogelsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2009Patrick Gizzi Abstract Novel histidine-based complexing surfactants, designed as AA-His-EOm -Cn, containing trifunctional moduli (peptidic/hydrophilic/hydrophobic) were synthesized by a modular step-by-step procedure, which allowed easy structural changes, and consequently correlations between their molecular structures and their self-assembling properties could be established. Thus, micelles or hydrogels could be obtained by simply modifying the hydrophobic tail lengths or the junction between the different moduli of the designed compounds. At low pH values, all compounds were surface active in aqueous solutions. At higher pH values, in the range 8,10, micellization took place for decyl compounds (n = 10), whereas hydrogelation occurred for longer chain lengths (n = 12, 14), and this, at very-low concentrations of surfactant (<0.3 wt.-%), could thus act as low molecular weight gelator (LMWG). The driving forces for gel formation were noncovalent intermolecular interactions such as ,-stacking and hydrophobic and hydrogen-bonding interactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Histidine and not tyrosine is required for the Peroxide-induced formation of haem to protein cross-linked myoglobinIUBMB LIFE, Issue 8-9 2007Brandon J. Reeder Abstract Peroxide-induced oxidative modifications of haem proteins such as myoglobin and haemoglobin can lead to the formation of a covalent bond between the haem and globin. These haem to protein cross-linked forms of myoglobin and haemoglobin are cytotoxic and have been identified in pathological conditions in vivo. An understanding of the mechanism of haem to protein cross-link formation could provide important information on the mechanisms of the oxidative processes that lead to pathological complications associated with the formation of these altered myoglobins and haemoglobins. We have re-examined the mechanism of the formation of haem to protein cross-link to test the previously reported hypothesis that the haem forms a covalent bond to the protein via the tyrosine 103 residue (Catalano, C. E., Choe, Y. S., Ortiz de Montellano, P. R., J. Biol. Chem. 1989, 10534 - 10541). Comparison of native horse myoglobin, recombinant sperm whale myoglobin and Tyr103 , Phe sperm whale mutant shows that, contrary to the previously proposed mechanism of haem to protein cross-link formation, the absence of tyrosine 103 has no impact on the formation of haem to protein cross-links. In contrast, we have found that engineered myoglobins that lack the distal histidine residue either cannot generate haem to protein cross-links or show greatly suppressed levels of modified protein. Moreover, addition of a distal histidine to myoglobin from Aplysia limacina, that naturally lacks this histidine, restores the haem protein's capacity to generate haem to protein cross-links. The distal histidine is, therefore, vital for the formation of haem to protein cross-link and we explore this outcome. [source] The Physicochemical Quality Characteristics of Charcoal Grilled MackerelsJOURNAL OF FOOD SCIENCE, Issue 3 2002M-Y. Kim ABSTRACT: : The effects of different fuel sources used in grilling on the physicochemical and sensory characteristics of mackerel were investigated. Oak and sawdust charcoals were used as fuel sources. The content of saturated fatty acids was increased during grilling. Histidine was the most predominant amino acid; grilling significantly increased glutamic acid. Mackerel shows a high inosine 5,-monophosphate content that is increased during grilling. Oak charcoal and sawdust charcoal contained high levels of potassium and sodium, respectively. Potassium content was increased at the surface muscle of oak charcoal grilled mackerel (OM). The flavor preference for OM was significantly (p < 0.05%) higher than for sawdust charcoal grilled mackerel. These results indicate that physicochemical and sensory properties of grilled foods can be affected by the fuel source. [source] Melatonin protects kidney grafts from ischemia/reperfusion injury through inhibition of NF-kB and apoptosis after experimental kidney transplantationJOURNAL OF PINEAL RESEARCH, Issue 4 2009Zhanqing Li Abstract:, Free radicals are involved in pathophysiology of ischemia/reperfusion injury (IRI). Melatonin is a potent scavenger of reactive oxygen and nitrogen species. Thus, this study was designed to elucidate its effects in a model of rat kidney transplantation. Twenty Lewis rats were randomly divided into 2 groups (n = 10 animals each). Melatonin (50 mg/kg BW) dissolved in 5 mL milk was given to one group via gavage 2 hr before left donor nephrectomy. Controls were given the same volume of milk only. Kidney grafts were then transplanted into bilaterally nephrectomized syngeneic recipients after 24 hr of cold storage in Histidine,Tryptophan,Ketoglutarate solution. Both graft function and injury were assessed after transplantation through serum levels of blood urea nitrogen (BUN), creatinine, transaminases, and lactate dehydrogenase (LDH). Biopsies were taken to evaluate tubular damage, the enzymatic activity of superoxide dismutase (SOD) and lipid hydroperoxide (LPO), and the expression of NF-kBp65, inducible nitric oxide synthase (iNOS), caspase-3 as indices of oxidative stress, necrosis, and apoptosis, respectively. Melatonin improved survival (P < 0.01) while decreasing BUN, creatinine, transaminases, and LDH values up to 39,71% (P < 0.05). Melatonin significantly reduced the histological index for tubular damage, induced tissue enzymatic activity of SOD while reducing LPO. At the same time, melatonin down-regulated the expression of NF-kBp65, iNOS, and caspase-3. In conclusion, donor preconditioning with melatonin protected kidney donor grafts from IRI-induced renal dysfunction and tubular injury most likely through its anti-oxidative, anti-apoptotic and NF-kB inhibitory capacity. [source] Histidine,Tryptophan,Ketoglutarate (HTK) Is Associated with Reduced Graft Survival in Deceased Donor Livers, Especially Those Donated After Cardiac DeathAMERICAN JOURNAL OF TRANSPLANTATION, Issue 2 2009Z. A. Stewart Single-center studies have reported that liver allograft survival is not affected by preservation in histidine,tryptophan,ketoglutarate (HTK) versus University of Wisconsin (UW) solution. We analyzed the UNOS database of liver transplants performed from July, 2004, through February, 2008, to determine if preservation with HTK (n = 4755) versus UW (n = 12 673) impacted graft survival. HTK preservation of allografts increased from 16.8% in 2004 to 26.9% in 2008; this was particularly striking among donor after cardiac death (DCD) allografts, rising from 20.7% in 2004 to 40.9% in 2008. After adjusting for donor, recipient and graft factors that affect graft survival, HTK preservation was associated with an increased risk of graft loss (HR 1.14, p = 0.002), especially with DCD allografts (HR 1.44, P = 0.025) and those with cold ischemia time over 8 h (HR 1.16, P = 0.009). Furthermore, HTK preservation was associated with a 1.2-fold higher odds of early (< 30 days) graft loss as compared to UW preservation (OR 1.20, p = 0.012), with a more pronounced effect on allografts with cold ischemia time over 8 h (OR 1.31, p = 0.007), DCD allografts (OR 1.63, p = 0.09) and donors over 70 years (OR 1.67, p = 0.081). These results suggest that the increasing use of HTK for abdominal organ preservation should be reexamined. [source] Quantitative evaluation of His-tag purification and immunoprecipitation of tristetraprolin and its mutant proteins from transfected human cells,BIOTECHNOLOGY PROGRESS, Issue 2 2009Heping Cao Abstract Histidine (His)-tag is widely used for affinity purification of recombinant proteins, but the yield and purity of expressed proteins are quite different. Little information is available about quantitative evaluation of this procedure. The objective of this study was to evaluate His-tag procedure quantitatively and to compare it with immunoprecipitation using radiolabeled tristetraprolin (TTP), a zinc finger protein with anti-inflammatory property. Human embryonic kidney 293 cells were transfected with wild-type and nine mutant plasmids with single or multiple phosphorylation site mutation(s) in His-TTP. These proteins were expressed and mainly localized in the cytosol of transfected cells by immunocytochemistry and confocal microscopy. His-TTP proteins were purified by Ni-NTA beads with imidazole elution or precipitated by TTP antibodies from transfected cells after being labeled with [32P]-orthophosphate. The results showed that (1) His-tag purification was more effective than immunoprecipitation for TTP purification; (2) mutations in TTP increased the yield of His-TTP by both purification procedures; and (3) mutations in TTP increased the binding affinity of mutant proteins for Ni-NTA beads. These findings suggest that bioengineering phosphorylation sites in proteins can increase the production of recombinant proteins. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] ChemInform Abstract: A New Receptor Molecule for Lysine and Histidine in Water: Strong Binding of Basic Amino Acid Esters by a Macrocyclic Host.CHEMINFORM, Issue 37 2001Thomas Grawe Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] The Possible Influence of L -Histidine on the Origin of the First Peptides on the Primordial EarthCHEMISTRY & BIODIVERSITY, Issue 6 2006Hannes Reiner Abstract One of the most unsettled problems of prebiotic evolution and the origin of life is the explanation why one enantiomeric form of biomolecules prevailed. In the experiments presented in this paper, the influence of L -histidine on the peptide formation in the Salt-Induced Peptide Formation (SIPF) reaction of the enantiomeric forms of valine, proline, serine, lysine, and tryptophan, and the catalytic effects in this first step toward the first building blocks of proteins on the primordial earth were investigated. In the majority of the produced dipeptides, a remarkable increase of yields was shown, and the preference of the L - amino acids in the peptide formation in most cases cannot be denied. In summary, our data provide further experimental evidence for the plausibility of the SIPF reaction and point at a possible important role of L -histidine in the chemical evolution on the primordial earth. [source] Fabrication of Ultrathin Films with Large Third-Order Nonlinear Optical PropertiesCHEMPHYSCHEM, Issue 3 2005Li Jiang Abstract An ultrathin composite film containing anionic Ag-His complexes (His: L -Histidine) and oppositely charged BH-PPV was fabricated by means of the electrostatic layer-by-layer self-assembly technique. UV/Vis spectra showed a continuous deposition process of Ag-His complexes and BH-PPV. The film structure was characterized by using small-angle X-ray diffraction, AFM, and SEM. The nonlinear optical properties of the ultrathin film were studied by using the Z -scan technique with a laser duration of 8 ns at a wavelength of 532 nm. The film sample exhibited a strong nonlinear saturated absorption, with an ,2value of ,3.9×10,5m,W,1and a self-defocusing effect with an n2value of ,4.78×10,12m2,W,1. [source] Heterodimers of Histidine and Amantadine as Inhibitors for Wild Type and Mutant M2 Channels of Influenza ACHINESE JOURNAL OF CHEMISTRY, Issue 8 2010Wenjuan Zhang Abstract Inhibitors bearing the imidazole, adamantane and related structures were synthesized and tested against WT, S31N and S31N-L26I mutant M2 channels. Although amantadine (1) only inhibited WT M2 channel, compound 6 containing the imidazole and adamantane groups showed good inhibitory activity to WT and mutant M2 channels. The stereochemistry and basic pKa of , -amine are important for the activity of inhibitors and our data showed that derivatives of natural histidine are more active for M2 channels than those of unnatural histidine. The significance of our present results is that we have established a prospective strategy of drug discovery of WT and mutant M2 channels against influenza A. [source] Abnormal myelin formation in rhizomelic chondrodysplasia punctata type 2 (DHAPAT-deficiency)DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 7 2000László Sztriha MD PhD The case of a Yemeni girl with isolated peroxisomal acyl-CoA:dihydroxyacetonephosphateacyltransferase (DHAPAT) deficiency is reported. She had rhizomelic chondrodysplasia punctata, microcephaly, failure to thrive, delayed motor and mental development, and spastic quadriplegia. Deficient de novo plasmalogen synthesis in her fibroblasts as a result of low DHAPAT activity was found, while her very-long-chain fatty acid profile, phytanic acid concentration, alkyl-dihydroxyacetonephosphate synthase (alkyl-DHAP synthase) activity, and peroxisomal 3-ketoacyl-CoA thiolase protein were normal. A mutation in her DHAPAT complementary DNA resulted in the substitution of an arginine residue in the protein at position 211 by a histidine (R211H). Magnetic resonance imaging showed abnormal white matter signal in the centrum semiovale involving the arcuate fibers, while the corpus callosum was normal. DHAPAT and alkyl-DHAP synthase initiate the synthesis of plasmalogens, which are major constituents of myelin phospholipids. The reported girl's abnormal formation of myelin is probably related to the inadequacy of plasmalogen biosynthesis, which is likely to be due to deficient DHAPAT activity. [source] Autoradiographic observations on developing and growing claws of reptilesACTA ZOOLOGICA, Issue 2 2010Lorenzo Alibardi Abstract Alibardi, L. 2010. Autoradiographic observations on developing and growing claws of reptiles. ,Acta Zoologica (Stockholm) 91: 233,241 The present qualitative autoradiographic analysis aims to present the main features of morphogenesis and growth of claws in reptiles. Lizard embryos treated with tritiated thymidine reveal that epidermal cell proliferation in terminal digits is prevalent in the dorsal side and gives origin to the curved unguis of the claw. Less proliferation occurs in the ventral side of the digit tip where the concave sub-unguis is derived. Adult claws of a turtle show that thymidine-labelled cells are present along most of the epidermis of the claw, especially at the claw tip. Also, injection of tritiated histidine and proline, indicating active protein synthesis, confirm autoradiographic labelling along most of the epidermis of claws, in particular at the apical tip. The present study indicates that proximal matrix regions, as have been described in mammalian nails, are absent in reptiles. This pattern of claw growth probably derives from that of terminal digital scales. In fact reptilian (and avian) claws are formed from a modification of scales, a different condition from that present in mammals. [source] Improved Voltammetric Response of L -Tyrosine on Multiwalled Carbon Nanotubes-Ionic Liquid Composite Coated Glassy Electrodes in the Presence of Cupric IonELECTROANALYSIS, Issue 19 2008Liqin Liu Abstract L -Tyrosine can exhibit a small anodic peak on multiwalled carbon nanotubes (MWCNTs) coated glassy carbon electrodes (GCE). At pH,5.5 its peak potential is 0.70,V (vs. SCE). When an ionic liquid (i.e., 1-octyl-3-methylimidazolium hexafluorophosphate, [omim][PF6]) is introduced on the MWCNT coat, the peak becomes bigger. Furthermore, in the presence of Cu2+ ion the anodic peak of L -tyrosine increases further due to the formation of Cu2+ - L -tyrosine complex, while the peak potential keeps unchanged. Therefore, a sensitive voltammetry based on the oxidation of Cu2+ - L -tyrosine complex on MWCNTs-[omim][PF6] composite coated electrode is developed for L -tyrosine. Under the optimized conditions, the anodic peak current is linear to L -tyrosine concentration in the range of 1×10,8,5×10,6 M, and the detection limit is 8×10,9 M. The modified electrode shows good reproducibility and stability. In addition, the voltammetric behavior of other amino acids is explored. It is found that among them tryptophan (Trp) and histidine (His) can also produce sensitive anodic peak under same experimental conditions, and their detection limits are 4×10,9 M and 4×10,6 M, respectively. [source] Determination of 1-methylhistidine and 3-methylhistidine by capillary and chip electrophoresis with contactless conductivity detectionELECTROPHORESIS, Issue 13 2007Petr T, ma Dr. Abstract CE with capacitively coupled contactless detection (C4D) was used to determine 3-methylhistidine (3-MH) and 1-methylhistidine (1-MH). The C4D response to 3-MH was studied in a BGE consisting of 500,mM acetic acid and ammonia at varying concentration and the results were compared with the theory. Complete separation of a model mixture of 3-MH, 1-MH, and histidine (His) was attained in two optimized BGEs, one containing 500,mM HAc, 20,mM NH4OH, and 0.1 % m/v hydroxyethylcellulose (HEC), pH,3.4 (I) and the other consisting of 100,mM morpholinoethanesulfonic acid (MES), 25,mM LiOH, and 0.1 % m/v HEC, pH,5.5 (II). These optimized BGEs were tested in CE/C4D analyses of urine. Promising results were obtained for separation and determination of 3-MH, 1-MH, and His on a silicon microchip, using aluminum strips as the C4D electrodes; the three analytes were baseline-separated within less than 30,s with a separation channel effective length of 38,mm. The LOD were satisfactory and amounted to 26.4,,M for 3-MH and 18.3,,M for 1-MH. [source] Manganese speciation in human cerebrospinal fluid using CZE coupled to inductively coupled plasma MSELECTROPHORESIS, Issue 9 2007Bernhard Michalke Dr. Abstract The neurotoxic effects of manganese (Mn) at elevated concentrations are well known. This raises the question, which of the Mn species can cross neural barriers and appear in cerebrospinal fluid (CSF). CSF is the last matrix in a living human organism available for analysis before a compound reaches the brain cells and therefore it is assumed to reflect best the internal exposure of brain tissue to Mn species. A previously developed CE method was modified for separation of albumin, histidine, tyrosine, cystine, fumarate, malate, inorganic Mn, oxalacetate, ,-keto-glutarate, nicotinamide-dinucleotide (NAD), citrate, adenosine, glutathione, and glutamine. These compounds are supposed in the literature to act as potential Mn carriers. In a first attempt, these compounds were analyzed by CZE-UV to check whether they are present in CSF. The CZE-UV method was simpler than the coupled CZE-inductively coupled plasma (ICP)-dynamic reaction cell (DRC)-MS method and it was therefore chosen to obtain a first overview information. In a second step, the coupled method (CZE-ICP-DRC-MS) was used to analyze, in detail, which of the compounds found in CSF by CZE-UV were actually bound to Mn. Finally, 13 Mn species were monitored in CSF samples, most of them being identified: Mn-histidine, Mn-fumarate, Mn-malate, inorganic Mn, Mn-oxalacetate, Mn-,-keto glutarate, Mn-carrying NAD, Mn-citrate and Mn-adenosine. By far the most abundant Mn species was Mn-citrate showing a concentration of 0.7,±,0.13,µg,Mn/L. Interestingly, several other Mn species can be related to the citric acid cycle. [source] Cold adaptation in the marine bacterium, Sphingopyxis alaskensis, assessed using quantitative proteomicsENVIRONMENTAL MICROBIOLOGY, Issue 10 2010Lily Ting Summary The cold marine environment constitutes a large proportion of the Earth's biosphere. Sphingopyxis alaskensis was isolated as a numerically abundant bacterium from several cold marine locations, and has been extensively studied as a model marine bacterium. Recently, a metabolic labelling platform was developed to comprehensively identify and quantify proteins from S. alaskensis. The approach incorporated data normalization and statistical validation for the purpose of generating highly confident quantitative proteomics data. Using this approach, we determined quantitative differences between cells grown at 10°C (low temperature) and 30°C (high temperature). Cold adaptation was linked to specific aspects of gene expression: a dedicated protein-folding system using GroESL, DnaK, DnaJ, GrpE, SecB, ClpB and PPIase; polyhydroxyalkanoate-associated storage materials; a link between enzymes in fatty acid metabolism and energy generation; de novo synthesis of polyunsaturated fatty acids in the membrane and cell wall; inorganic phosphate ion transport by a phosphate import PstB homologue; TonB-dependent receptor and bacterioferritin in iron homeostasis; histidine, tryptophan and proline amino acid metabolism; and a large number of proteins without annotated functions. This study provides a new level of understanding on how important marine bacteria can adapt to compete effectively in cold marine environments. This study is also a benchmark for comparative proteomic analyses with other important marine bacteria and other cold-adapted organisms. [source] Lack of CbrB in Pseudomonas putida affects not only amino acids metabolism but also different stress responses and biofilm developmentENVIRONMENTAL MICROBIOLOGY, Issue 6 2010Cristina I. Amador Summary The CbrAB two-component system has been described in certain species of Pseudomonads as a global regulatory system required for the assimilation of several amino acids (e.g. histidine, proline or arginine) as carbon or carbon and nitrogen sources. In this work, we used global gene expression and phenotypic analyses to characterize the roles of the CbrAB system in Pseudomonas putida. Our results show that CbrB is involved in coordination with the nitrogen control system activator, NtrC, in the uptake and assimilation of several amino acids. In addition, CbrB affects other carbon utilization pathways and a number of apparently unrelated functions, such as chemotaxis, stress tolerance and biofilm development. Based on these new findings, we propose that CbrB is a high-ranked element in the regulatory hierarchy of P. putida that directly or indirectly controls a variety of metabolic and behavioural traits required for adaptation to changing environmental conditions. [source] Development of Amygdaloid Kindling in Histidine Decarboxylase,deficient and Histamine H1 Receptor,deficient MiceEPILEPSIA, Issue 4 2004Tadashi Hirai Summary: Purpose: This study attempted to clarify the role of histamine or histamine H1 receptors in the development of amygdaloid kindling by using histidine decarboxylase (HDC)-deficient and histamine H1 receptor (H1R)-deficient mice. Methods: Under pentobarbital anesthesia, mice were fixed to a stereotaxic apparatus, and bipolar electrodes were implanted into the right amygdala. Electrodes were connected to a miniature receptacle, which was embedded in the skull with dental cement. A bipolar electroencephalogram was recorded; bipolar stimulation of the amygdala was applied every day with a constant-current stimulator and continued until a generalized convulsion was obtained. Results: The development of amygdaloid kindling in HDC-deficient and H1R-deficient mice was significantly accelerated compared with that in their respective wild-type mice. In addition, the afterdischarge (AD) duration and generalized seizure duration in HDC-deficient and H1R-deficient mice were prolonged. Intraperitoneal injection of histidine resulted in an inhibition of amygdaloid kindled seizures in wild-type mice at doses that caused an increase in the histamine contents of the brain. However, no significant effect was observed with histidine in H1R-deficient mice at the same dose. Conclusions: These findings suggest that histaminergic mechanisms through H1 receptors play a crucial role not only in amygdaloid kindled seizures but also in the development of amygdaloid kindling. [source] Binding of Oxovanadium(IV) to Tripeptides Containing Histidine and Cysteine Residues and Its Biological Implication in the Transport of Vanadium and Insulin-Mimetic CompoundsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2005Eugenio Garribba Abstract The complexation of VIVO ion with three tripeptides of biological importance containing L -histidine or L -cysteine (HisGlyGly, GlyGlyHis and GlyGlyCys) has been studied. This study was performed in aqueous solution by the combined application of potentiometric and spectroscopic (electronic absorption and EPR) techniques. The results indicate that these oligopeptides, if a ligand-to-metal molar ratio of 10 or 15 is used, can keep VIVO ion in solution until the deprotonation of the amide group with the donor set (NH2, CO, Nimax) for HisGlyGly or (COO,, CO) for GlyGlyHis and GlyGlyCys. In all the systems, at pH values around neutrality, a VOLH,2 species is formed with an (NH2, N,, N,, COO,) donor set for HisGlyGly, (NH2, N,, N,, Nim) for GlyGlyHis and (NH2, N,,N,, S,) for GlyGlyCys. These species, and those with onedeprotonated amide group coordinated to the VIVO ion, can be detected by EPR spectroscopy. The N,(amide) contribution to the hyperfine coupling constant along the z axis, Az, depends on the total charge of the donor atoms in the equatorial plane. The participation of albumin in the transport of vanadium and insulin-mimetic VIVO compounds is reconsidered based on these results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Funnel Complexes with CoII and NiII: New Probes into the Biomimetic Coordination Ability of the Calix[6]arene-Based Tris(imidazole) SystemEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2004Olivier Sénčque Abstract The coordination properties of the calix[6]arene-based tris(imidazole) ligand X6Me3Imme3 were further explored with CoII and NiII. This imidazole system stabilizes tetrahedral mononuclear CoII complexes with an exchangeable fourth exogenous ligand (water, alcohol, amide) located at the heart of the hydrophobic calixarene cavity. With a weak donor ligand such as a nitrile, both four-coordinate tetrahedral and five-coordinate trigonal bipyramidal complexes were obtained. The latter contains a second nitrile molecule trans to the included guest nitrile. These complexes were characterized in solution as well as in the solid state. The NiII complexes are square-based pyramidal five-coordinate edifices with a guest nitrile inside the cavity and a water molecule outside. A comparison with previously described ZnII and CuII complexes emphasizes the flexibility of this ligand. A comparison with carbonic anhydrase, a mononuclear zinc enzyme with a tris(histidine) coordination core, shows that X6Me3Imme3 displays many structural features of this enzyme except for the cis coordination of the exogenous ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Molecular Tailored Histidine-Based Complexing Surfactants: From Micelles to HydrogelsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2009Patrick Gizzi Abstract Novel histidine-based complexing surfactants, designed as AA-His-EOm -Cn, containing trifunctional moduli (peptidic/hydrophilic/hydrophobic) were synthesized by a modular step-by-step procedure, which allowed easy structural changes, and consequently correlations between their molecular structures and their self-assembling properties could be established. Thus, micelles or hydrogels could be obtained by simply modifying the hydrophobic tail lengths or the junction between the different moduli of the designed compounds. At low pH values, all compounds were surface active in aqueous solutions. At higher pH values, in the range 8,10, micellization took place for decyl compounds (n = 10), whereas hydrogelation occurred for longer chain lengths (n = 12, 14), and this, at very-low concentrations of surfactant (<0.3 wt.-%), could thus act as low molecular weight gelator (LMWG). The driving forces for gel formation were noncovalent intermolecular interactions such as ,-stacking and hydrophobic and hydrogen-bonding interactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Non-enzymatic hydrolysis of fluorescein diacetate (FDA) in a Mediterranean oak (Quercus ilex L.) litterEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2008E. Alarcón-Gutiérrez Summary We show the presence of interfering substances when the total microbial activity in litter samples is measured with fluorescein diacetate (FDA), and we propose some methodological modifications to avoid such interference. Three distinct litter layers (the OhLn, the OhLv and the OhLf) of evergreen oak (Quercus ilex L.) were characterized by 13C CPMAS NMR and the spectra show that the recalcitrant aromatic and phenolic compounds increase with the degree of degradation of litter. A wide range of sources of interference in the hydrolysis of FDA was found. To understand the origin of this interference, sterilized litter materials (i.e. ,-irradiated or autoclaved) and a wide range of organic substances (i.e. amino acids, glucose, sorbitol and organic humic acids) were investigated. Insignificant differences on the FDA hydrolysis activity (FDA activity) were found in the ,-irradiated and non-irradiated OhLn litter, indicating that ,-irradiation does not destroy enzymes. Conversely, after heat-sterilization of litter, samples showed FDA activity corresponding to 60, 34.8 and 30.8% (in the OhLn, the OhLv and the OhLf layers, respectively) of that of control litters. This indicates the presence of non-enzymatic interfering substances in the FDA assays. As the humification and litter depth increased, hydrolysis of FDA due to interferences decreased, indicating degradation and/or chelation of interfering substances. We hypothesize that lysine, arginine, histidine and cysteine are mainly responsible for the hydrolysis of FDA. We suggest that the use of phosphate buffer (50 mm, pH 7.0) with incubation <,30 minutes, in combination with a temperature between 30 and 40°C, produces insignificant interference in the determination of the final FDA activity in litter samples. [source] Thermosynechoccus elongatus DpsA binds Zn(II) at a unique three histidine-containing ferroxidase center and utilizes O2 as iron oxidant with very high efficiency, unlike the typical Dps proteinsFEBS JOURNAL, Issue 4 2010Flaminia Alaleona The cyanobacterium Thermosynechococcus elongatus is one the few bacteria to possess two Dps proteins, DpsA-Te and Dps-Te. The present characterization of DpsA-Te reveals unusual structural and functional features that differentiate it from Dps-Te and the other known Dps proteins. Notably, two Zn(II) are bound at the ferroxidase center, owing to the unique substitution of a metal ligand at the A-site (His78 in place of the canonical aspartate) and to the presence of a histidine (His164) in place of a hydrophobic residue at a metal-coordinating distance in the B-site. Only the latter Zn(II) is displaced by incoming iron, such that Zn(II),Fe(III) complexes are formed upon oxidation, as indicated by absorbance and atomic emission spectroscopy data. In contrast to the typical behavior of Dps proteins, where Fe(II) oxidation by H2O2 is about 100-fold faster than by O2, in DpsA-Te the ferroxidation efficiency of O2 is very high and resembles that of H2O2. Oxygraphic experiments show that two Fe(II) are required to reduce O2, and that H2O2 is not released into solution at the end of the reaction. On this basis, a reaction mechanism is proposed that also takes into account the formation of Zn(II),Fe(III) complexes. The physiological significance of the DpsA-Te behavior is discussed in the framework of a possible localization of the protein at the thylakoid membranes, where photosynthesis takes place, with the consequent increased formation of reactive oxygen species. Structured digital abstract ,,MINT-7312099: DpsA (uniprotkb:Q8DL82) and DpsA (uniprotkb:Q8DL82) bind (MI:0407) by x-ray crystallography (MI:0114) [source] Putative reaction mechanism of heterologously expressed octopine dehydrogenase from the great scallop, Pecten maximus (L)FEBS JOURNAL, Issue 24 2007Andre Müller cDNA for octopine dehydrogenase (ODH) from the adductor muscle of the great scallop, Pecten maximus, was cloned using 5,- and 3,-RACE. The cDNA comprises an ORF of 1197 nucleotides and the deduced amino acid sequence encodes a protein of 399 amino acids. ODH was heterologously expressed in Escherichia coli with a C-terminal penta His-tag. ODH,5His was purified to homogeneity using metal,chelate affinity chromatography and Sephadex G-100 gel filtration. Recombinant ODH had kinetic properties similar to those of wild-type ODH isolated from the scallop's adductor muscle. Site-directed mutagenesis was used to elucidate the involvement of several amino acid residues for the reaction catalyzed by ODH. Cys148, which is conserved in all opine dehydrogenases known to date, was converted to serine or alanine, showing that this residue is not intrinsically important for catalysis. His212, Arg324 and Asp329, which are also conserved in all known opine dehydrogenase sequences, were subjected to site-directed mutagenesis. Modification of these residues revealed their importance for the catalytic activity of the enzyme. Conversion of each of these residues to alanine resulted in strong increases in Km and decreases in kcat values for pyruvate and l -arginine, but had little effect on the Km and kcat values for NADH. Assuming a similar structure for ODH compared with the only available structure of a bacterial opine dehydrogenase, these three amino acids may function as a catalytic triad in ODH similar to that found in lactate dehydrogenase or malate dehydrogenase. The carboxyl group of pyruvate is then stabilized by Arg324. In addition to orienting the substrate, His212 will act as an acid,base catalyst by donating a proton to the carbonyl group of pyruvate. The acidity of this histidine is further increased by the proximity of Asp329. [source] Comparative metal binding and genomic analysis of the avian (chicken) and mammalian metallothioneinFEBS JOURNAL, Issue 3 2006Laura Villarreal Chicken metallothionein (ckMT) is the paradigm for the study of metallothioneins (MTs) in the Aves class of vertebrates. Available literature data depict ckMT as a one-copy gene, encoding an MT protein highly similar to mammalian MT1. In contrast, the MT system in mammals consists of a four-member family exhibiting functional differentiation. This scenario prompted us to analyse the apparently distinct evolutionary patterns followed by MTs in birds and mammals, at both the functional and structural levels. Thus, in this work, the ckMT metal binding abilities towards Zn(II), Cd(II) and Cu(I) have been thoroughly revisited and then compared with those of the mammalian MT1 and MT4 isoforms, identified as zinc- and copper-thioneins, respectively. Interestingly, a new mechanism of MT dimerization is reported, on the basis of the coordinating capacity of the ckMT C-terminal histidine. Furthermore, an evolutionary study has been performed by means of in silico analyses of avian MT genes and proteins. The joint consideration of the functional and genomic data obtained questions the two features until now defining the avian MT system. Overall, in vivo and in vitro metal-binding results reveal that the Zn(II), Cd(II) and Cu(I) binding abilities of ckMT lay between those of mammalian MT1 and MT4, being closer to those of MT1 for the divalent metal ions but more similar to those of MT4 for Cu(I). This is consistent with a strong functional constraint operating on low-copy number genes that must cope with differentiating functional limitation. Finally, a second MT gene has been identified in silico in the chicken genome, ckMT2, exhibiting all the features to be considered an active coding region. The results presented here allow a new insight into the metal binding abilities of warm blooded vertebrate MTs and their evolutionary relationships. [source] The catalytic role of the distal site asparagine-histidine couple in catalase-peroxidasesFEBS JOURNAL, Issue 5 2003Christa Jakopitsch Catalase-peroxidases (KatGs) are unique in exhibiting an overwhelming catalase activity and a peroxidase activity of broad specificity. Similar to other peroxidases the distal histidine in KatGs forms a hydrogen bond with an adjacent conserved asparagine. To investigate the catalytic role(s) of this potential hydrogen bond in the bifunctional activity of KatGs, Asn153 in Synechocystis KatG was replaced with either Ala (Asn153,Ala) or Asp (Asn153,Asp). Both variants exhibit an overall peroxidase activity similar with wild-type KatG. Cyanide binding is monophasic, however, the second-order binding rates are reduced to 5.4% (Asn153,Ala) and 9.5% (Asn153,Asp) of the value of native KatG [(4.8 ± 0.4) × 105 m,1·s,1 at pH 7 and 15 °C]. The turnover number of catalase activity of Asn153,Ala is 6% and that of Asn153,Asp is 16.5% of wild-type activity. Stopped-flow analysis of the reaction of the ferric forms with H2O2 suggest that exchange of Asn did not shift significantly the ratio of rates of H2O2 -mediated compound I formation and reduction. Both rates seem to be reduced most probably because (a) the lower basicity of His123 hampers its function as acid-base catalyst and (b) Asn153 is part of an extended KatG-typical H-bond network, the integrity of which seems to be essential to provide optimal conditions for binding and oxidation of the second H2O2 molecule necessary in the catalase reaction. [source] Proximal ligand motions in H93G myoglobinFEBS JOURNAL, Issue 19 2002Stefan Franzen Resonance Raman spectroscopy has been used to observe changes in the iron,ligand stretching frequency in photoproduct spectra of the proximal cavity mutant of myoglobin H93G. The measurements compare the deoxy ferrous state of the heme iron in H93G(L), where L is an exogenous imidazole ligand bound in the proximal cavity, to the photolyzed intermediate of H93G(L)*CO at 8 ns. There are significant differences in the frequencies of the iron,ligand axial out-of-plane mode ,(Fe,L) in the photoproduct spectra depending on the nature of L for a series of methyl-substituted imidazoles. Further comparison was made with the proximal cavity mutant of myoglobin in the absence of exogenous ligand (H93G) and the photoproduct of the carbonmonoxy adduct of H93G (H93G-*CO). For this case, it has been shown that H2O is the axial (fifth) ligand to the heme iron in the deoxy form of H93G. The photoproduct of H93G-*CO is consistent with a transiently bound ligand proposed to be a histidine. The data presented here further substantiate the conclusion that a conformationally driven ligand switch exists in photolyzed H93G-*CO. The results suggest that ligand conformational changes in response to dynamic motions of the globin on the nanosecond and longer time scales are a general feature of the H93G proximal cavity mutant. [source] Coordination chemistry of iron(III),porphyrin,antibody complexesFEBS JOURNAL, Issue 2 2002Influence on the peroxidase activity of the axial coordination of an imidazole on the iron atom An artificial peroxidase-like hemoprotein has been obtained by associating a monoclonal antibody, 13G10, and its iron(III),,,,,,,,- meso -tetrakis(ortho -carboxyphenyl)porphyrin [Fe(ToCPP)] hapten. In this antibody, about two-thirds of the porphyrin moiety is inserted in the binding site, its ortho -COOH substituents being recognized by amino-acids of the protein, and a carboxylic acid side chain of the protein acts as a general acid base catalyst in the heterolytic cleavage of the O,O bond of H2O2, but no amino-acid residue is acting as an axial ligand of the iron. We here show that the iron of 13G10,Fe(ToCPP) is able to bind, like that of free Fe(ToCPP), two small ligands such as CN,, but only one imidazole ligand, in contrast to to the iron(III) of,Fe(ToCPP) that binds two. This phenomenon is general for a series of monosubstituted imidazoles, the 2- and 4-alkyl-substituted imidazoles being the best ligands, in agreement with the hydrophobic character of the antibody binding site. Complexes of antibody 13G10 with less hindered iron(III),tetraarylporphyrins bearing only one [Fe(MoCPP)] or two meso-[ortho -carboxyphenyl] substituents [Fe(DoCPP)] also bind only one imidazole. Finally, peroxidase activity studies show that imidazole inhibits the peroxidase activity of 13G10,Fe(ToCPP) whereas it increases that of 13G10,Fe(DoCPP). This could be interpreted by the binding of the imidazole ligand on the iron atom which probably occurs in the case of 13G10,Fe(ToCPP) on the less hindered face of the porphyrin, close to the catalytic COOH residue, whereas in the case of 13G10,Fe(DoCPP) it can occur on the other face of the porphyrin. The 13G10,Fe(DoCPP),imidazole complex thus constitutes a nice artificial peroxidase-like hemoprotein, with the axial imidazole ligand of the iron mimicking the proximal histidine of peroxidases and a COOH side chain of the antibody acting as a general acid-base catalyst like the distal histidine of peroxidases does. [source] Involvement of Gln937 of Streptococcus downei GTF-I glucansucrase in transition-state stabilizationFEBS JOURNAL, Issue 13 2000Vincent Monchois Multiple alignment of deduced amino-acid sequences of glucansucrases (glucosyltransferases and dextransucrases) from oral streptococci and Leuconostoc mesenteroides has shown them to share a well-conserved catalytic domain. A portion of this domain displays homology to members of the ,-amylase family (glycoside hydrolase family 13), which all have a (,/,)8 barrel structure. In the glucansucrases, however, the ,-helix and ,-strand elements are circularly permuted with respect to the order in family 13. Previous work has shown that amino-acid residues contributing to the active site of glucansucrases are situated in structural elements that align with those of family 13. In ,-amylase and cyclodextrin glucanotransferase, a histidine residue has been identified that acts to stabilize the transition state, and a histidine is conserved at the corresponding position in all other members of family 13. In all the glucansucrases, however, the aligned position is occupied by glutamine. Mutants of glucosyltransferase I were constructed in which this glutamine, Gln937, was changed to histidine, glutamic acid, aspartic acid, asparagine or alanine. The effects on specific activity, ability to form glucan and ability to transfer glucose to a maltose acceptor were examined. Only histidine could substitute for glutamine and maintain Michaelis,Menten kinetics, albeit at a greatly reduced kcat, showing that Gln937 plays a functionally equivalent role to the histidine in family 13. This provides additional evidence in support of the proposed alignment of the (,/,)8 barrel structures. Mutation at position 937 altered the acceptor reaction with maltose, and resulted in the synthesis of novel gluco-oligosaccharides in which ,1,3-linked glucosyl units are joined sequentially to maltose. [source] | ||||||||||||||||||||||||||||||||||||||||||||||