Prosthetic Groups (prosthetic + groups)

Distribution by Scientific Domains


Selected Abstracts


Early Polarographic Studies on Proteins

ELECTROANALYSIS, Issue 13-14 2004
Michael Heyrovsky
Abstract The first effects of proteins observed with the dropping mercury electrode were catalytic, due to evolution of hydrogen in weakly alkaline solutions. Catalytic lowering of hydrogen overvoltage in presence of cobalt ions, the so-called Brdicka reaction, became the main means for polarographic study of proteins. Apart from that, polarography has been used for following proteins in their adsorption on the electrode surface, in their anodic reaction with mercury at positive potentials, in reduction of the disulfidic bonds of their components, in their complexation with metallic ions in the solution, in electrode reactions of their prosthetic groups and in antigen-antibody interactions. Our review is limited to applications of the dropping mercury electrode. [source]


Labelling of octreotide using 76Br-prosthetic groups

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 8 2001
Ulrika Yngve
Abstract A method for labelling the octapeptide octreotide (D,Phe,Cys,Phe,D,Trp,Lys,Thr,Cys,Thr(ol)) with the positron emitting 76Br (T1/2=16 h) is presented. , -Boc-protected octreotide was conjugated to N,succinimidyl 4-[76Br]bromobenzoate 1 and N,succinimidyl 5-[76Br]bromo-3-pyridinecarboxylate 3 using microwave heating. The conjugates 4 and 5 were isolated in 50,55% radiochemical yield after the removal of the protecting Boc-group. Compound 3 was synthesised from the corresponding trimethylstannyl-precursor in 25% radiochemical yield. The synthesis of methyl-4-[76Br] bromobenzimidate 8 in 40% radiochemical yield from the precursor methyl-4-trimethylstannylbenzimidate is also described. Experiments were performed to react 8 with Boc-octreotide but no product was obtained. The binding-properties of 76Br-conjugates 4 and 5 to meningiomas were investigated using frozen section autoradiography. Compound 5 showed better binding properties than 4. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Redox enzymes in the plant plasma membrane and their possible roles

PLANT CELL & ENVIRONMENT, Issue 12 2000
A. Bérczi
ABSTRACT Purified plasma membrane (PM) vesicles from higher plants contain redox proteins with low-molecular-mass prosthetic groups such as flavins (both FMN and FAD), hemes, metals (Cu, Fe and Mn), thiol groups and possibly naphthoquinone (vitamin K1), all of which are likely to participate in redox processes. A few enzymes have already been identified: Monodehydroascorbate reductase (EC 1.6.5.4) is firmly bound to the cytosolic surface of the PM where it might be involved in keeping both cytosolic and, together with a b -type cytochrome, apoplastic ascorbate reduced. A malate dehydrogenase (EC 1.1.1.37) is localized on the inner side of the PM. Several NAD(P)H-quinone oxidoreductases have been purified from the cytocolic surface of the PM, but their function is still unknown. Different forms of nitrate reductase (EC 1.6.6.1,3) are found attached to, as well as anchored in, the PM where they may act as a nitrate sensor and/or contribute to blue-light perception, although both functions are speculative. Ferric-chelate-reducing enzymes (EC 1.6.99.13) are localized and partially characterized on the inner surface of the PM but they may participate only in the reduction of ferric-chelates in the cytosol. Very recently a ferric-chelate-reducing enzyme containing binding sites for FAD, NADPH and hemes has been identified and suggested to be a trans -PM protein. This enzyme is involved in the reduction of apoplastic iron prior to uptake of Fe2+ and is induced by iron deficiency. The presence of an NADPH oxidase, similar to the so-called respiratory burst oxidase in mammals, is still an open question. An auxin-stimulated and cyanide-insensitive NADH oxidase (possibly a protein disulphide reductase) has been characterized but its identity is still awaiting independent confirmation. Finally, the only trans -PM redox protein which has been partially purified from plant PM so far is a high-potential and ascorbate-reducible b -type cytochrome. In co-operation with vitamin K1 and an NAD(P)H-quinone oxidoreductase, it may participate in trans -PM electron transport. [source]


A cytochrome c fusion protein domain for convenient detection, quantification, and enhanced production of membrane proteins in Escherichia coli,Expression and characterization of cytochrome-tagged Complex I subunits

PROTEIN SCIENCE, Issue 8 2010
Tobias Gustavsson
Abstract Overproduction of membrane proteins can be a cumbersome task, particularly if high yields are desirable. NADH:quinone oxidoreductase (Complex I) contains several very large membrane-spanning protein subunits that hitherto have been impossible to express individually in any appreciable amounts in Escherichia coli. The polypeptides contain no prosthetic groups and are poorly antigenic, making optimization of protein production a challenging task. In this work, the C-terminal ends of the Complex I subunits NuoH, NuoL, NuoM, and NuoN from E. coli Complex I and the bona fide antiporters MrpA and MrpD were genetically fused to the cytochrome c domain of Bacillus subtilis cytochrome c550. Compared with other available fusion-protein tagging systems, the cytochrome c has several advantages. The heme is covalently bound, renders the proteins visible by optical spectroscopy, and can be used to monitor, quantify, and determine the orientation of the polypeptides in a plethora of experiments. For the antiporter-like subunits NuoL, NuoM, and NuoN and the real antiporters MrpA and MrpD, unprecedented amounts of holo-cytochrome fusion proteins could be obtained in E. coli. The NuoHcyt polypeptide was also efficiently produced, but heme insertion was less effective in this construct. The cytochrome c550 domain in all the fusion proteins exhibited normal spectra and redox properties, with an Em of about +170 mV. The MrpA and MrpD antiporters remained functional after being fused to the cytochrome c -tag. Finally, a his-tag could be added to the cytochrome domain, without any perturbations to the cytochrome properties, allowing efficient purification of the overexpressed fusion proteins. [source]


Identification of hemes and related cyclic tetrapyrroles by matrix-assisted laser desorption/ionization and liquid secondary ion mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2002
Hyung-Sun Youn
Mass spectrometry has proven to be a powerful technique applicable on trace amounts for the identification of known hemes and cyclic tetrapyrroles, and for providing critical information for the structure of new and novel versions. This report describes investigations of the practical limits of detection for such bioinorganic prosthetic groups, primarily by liquid secondary ion mass spectrometry (LSIMS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), including a survey of the utility of common matrices. The lower limit of detection under favorable conditions extends to low picomole amounts. Certain derivatization techniques, such as methyl esterification and chelation to zinc, both increase the sensitivity of analyses and provide spectroscopic signatures that enable heme/cyclic tetrapyrrole ions to be identified in the presence of contaminants. Copyright © 2002 John Wiley & Sons, Ltd. [source]


Phosphite-driven, [Cp*Rh(bpy)(H2O)]2+ -catalyzed reduction of nicotinamide and flavin cofactors: characterization and application to promote chemoenzymatic reduction reactions

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2010
Maria Mifsud Grau
Abstract The organometallic compound [Cp*Rh(bpy)(H2O)]2+ is a versatile catalyst for the in situ regeneration of reduced nicotinamides and flavins by catalyzing the electron transfer between the cathode or formate to the oxidized cofactors and prosthetic groups. In the present contribution we demonstrate the feasibility of phosphite as an alternative source of reducing equivalents. Thus, [Cp*Rh(bpy)(H2O)]2+ combines the catalytic activities of hydrogenases, formate and phosphite dehydrogenases in one catalyst. The catalytic properties of this novel regeneration approach are investigated, demonstrating that the general catalytic properties of [Cp*Rh(bpy)(H2O)]2+ are preserved. The principal applicability to promote alcoholdehydrogenase-catalyzed reduction reactions is demonstrated. Copyright © 2010 John Wiley & Sons, Ltd. [source]


Novel Controlling Mechanism of the Oxygen Affinity in Myoglobin With Isomeric Porphyrins

ARTIFICIAL ORGANS, Issue 2 2009
Saburo Neya
Abstract The biological function of the core modified porphyrin isomers such as porphycene, corrphycene, and hemiporphycene was examined. The iron complexes stoichiometrically coupled with apomyoglobin to afford stable holoproteins. The oxygen affinity of the reconstituted myoglobins (Mbs) changed over a 60 000-fold range depending on the molecular structure of the prosthetic groups. For instance, a corrphycene with electronegative substituents to the bipyrrole part reduced the oxygen affinity of Mb to P50 = 300 mm Hg while the porphycene-substituted Mb exhibited a P50 = 0.005 mm Hg. A notable increase in the oxygen delivery capacity of the corrphycene-substituted Mb was explained on the basis of the trapezoidal corrphycene shape that stabilizes the iron displacement from the macrocycle plane toward the proximal histidine. The above observations demonstrate that the core modified heme isomers serve as novel molecular tools to regulate the oxygen affinity of Mb. [source]


Dissecting membrane protein architecture: An annotation of structural complexity

BIOPOLYMERS, Issue 10 2009
Jaime Arce
Abstract ,-Helical membrane proteins exist in an anisotropic environment which strongly influences their folding, stability, and architecture, which is far more complex than a simple bundle of transmembrane helices, notably due to helix deformations, prosthetic groups and extramembrane structures. However, the role and the distribution of such heterogeneity in the supra molecular organization of membrane proteins remains poorly investigated. Using a nonredundant subset of ,-helical membrane proteins, we have annotated and analyze the statistics of several types of new elements such as incomplete helices, intramembrane loops, helical extensions of helical transmembrane domains, extracellular loops, and helices lying parallel to the membrane surface. The relevance of the annotation scheme was studied using residue composition, statistics, physical chemistry, and symmetry of their distribution in relation to the immediate membrane environment. Calculation of hydrophobicity using different scales show that different structural elements appear to have affinities coherent with their position in the membrane. Examination of the annotation scheme suggests that there is considerable information content in the amino acid compositions of the different elements suggesting that it might be useful for structural prediction. More importantly, the proposed annotation will help to decipher the complex hierarchy of interactions involved in membrane protein architecture. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 815,829, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]