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Redox Proteins (redox + protein)
Selected AbstractsTransient complexes of redox proteins: structural and dynamic details from NMR studiesJOURNAL OF MOLECULAR RECOGNITION, Issue 6 2004Miguel Prudêncio Abstract Redox proteins participate in many metabolic routes, in particular those related to energy conversion. Protein,protein complexes of redox proteins are characterized by a weak affinity and a short lifetime. Two-dimensional NMR spectroscopy has been applied to many redox protein complexes, providing a wealth of information about the process of complex formation, the nature of the interface and the dynamic properties of the complex. These studies have shown that some complexes are non-specific and exist as a dynamic ensemble of orientations while in other complexes the proteins assume a single orientation. The binding interface in these complexes consists of a small hydrophobic patch for specificity, surrounded by polar, uncharged residues that may enhance dissociation, and, in most complexes, a ring or patch of charged residues that enhances the association by electrostatic interactions. The entry and exit port of the electrons is located within the hydrophobic interaction site, ensuring rapid electron transfer from one redox centre to the next. Copyright © 2004 John Wiley & Sons, Ltd. [source] Redox proteins in mammalian cell death: an evolutionarily conserved function in mitochondria and prokaryotesCELLULAR MICROBIOLOGY, Issue 4 2003Vasu Punj Summary Mammalian cell mitochondria are believed to have prokaryotic ancestry. Mitochondria are not only the powerhouse of energy generation within the eukaryotic cell but they also play a major role in inducing apoptotic cell death through release of redox proteins such as cytochrome c and the apoptosis-inducing factor (AIF), a flavoprotein with NADH oxidase activity. Recent evidence indicates that some present day prokaryotes release redox proteins that induce apoptosis in mammalian cells through stabilization of the tumour suppressor protein p53. p53 interacts with mitochondria either directly or through activation of the genes for pro-apoptotic proteins such as Bax or NOXA or genes that encode redox enzymes responsible for the production of reactive oxygen species (ROS). The analogy between the ancient ancestors of present day bacteria, the mitochondria, and the present day bacteria with regard to their ability to release redox proteins for triggering mammalian cell death is an interesting example of functional conservation during the hundreds of millions of years of evolution. It is possible that the ancestors of the present day prokaryotes released redox proteins to kill the ancestors of the eukaryotes. During evolution of the mitochondria from prokaryotes as obligate endosymbionts, the mitochondria maintained the same functions to programme their own host cell death. [source] Direct Electrochemistry of Hemoglobin Immobilized on Colloidal Gold-Hydroxyapatite Nanocomposite for Electrocatalytic Detection of Hydrogen PeroxideELECTROANALYSIS, Issue 2 2009Juan You Abstract A novel nanocomposite of colloidal gold (GNPs) and hydroxyapatite nanotubes (Hap) was prepared for immobilization of a redox protein, hemoglobin (Hb), on glassy carbon electrode. The immobilized Hb showed fast direct electron transfer and excellent electrocatalytic behavior toward reduction of hydrogen peroxide. A synergic effect between GNPs and Hap for accelerating the surface electron transfer of Hb was observed, which led to a pair of redox peaks with a formal potential of (,340±2) mV at pH,7.0, and a new biosensor for hydrogen peroxide with a linear range from 0.5 to 25,,M and a limit of detection of 0.2,,M at 3,. Owing to the good biocompatibility of the nanocomposite, the biosensor exhibited good stability and acceptable reproducibility. The as-prepared nanocomposite film provided a good matrix for protein immobilization and biosensor preparation. [source] Binding of ligands originates small perturbations on the microscopic thermodynamic properties of a multicentre redox proteinFEBS JOURNAL, Issue 9 2005Carlos A. Salgueiro NMR and visible spectroscopy coupled to redox measurements were used to determine the equilibrium thermodynamic properties of the four haems in cytochrome c3 under conditions in which the protein was bound to ligands, the small anion phosphate and the protein rubredoxin with the iron in the active site replaced by zinc. Comparison of these results with data for the isolated cytochrome shows that binding of ligands causes only small changes in the reduction potentials of the haems and their pairwise interactions, and also that the redox-sensitive acid,base centre responsible for the redox,Bohr effect is essentially unaffected. Although neither of the ligands tested is a physiological partner of cytochrome c3, the small changes observed for the thermodynamic properties of cytochrome c3 bound to these ligands vs. the unbound state, indicate that the thermodynamic properties measured for the isolated protein are relevant for a physiological interpretation of the role of this cytochrome in the bioenergetic metabolism of Desulfovibrio. [source] Fabrication of Reactivated Biointerface for Dual-Controlled Reversible Immobilization of Cytochrome cADVANCED MATERIALS, Issue 43 2009Pengbo Wan A light or pH dual-responsive reactivated biointerface is fabricated using of photocontrolled reversible inclusion and exclusion reactions between photoresponsive azobenzene-containing self-assembled monolayer and pH-responsive poly(acrylic acid) polymer grafted with cyclodextrins. The dual-controlled reactivated biointerface can be employed for reversible immobilization of redox protein,Cytochrome c, triggered by dual external stimuli-light and pH. [source] Aqueous Stabilization and Self-Assembly of Graphene Sheets into Layered Bio-Nanocomposites using DNAADVANCED MATERIALS, Issue 31 2009Avinash J. Patil Stabilization of aqueous suspensions of graphene single sheets by single-stranded DNA is demonstrated using a range of physical methods. The negatively charged bio-functionalized graphene sheets are spontaneously assembled into layered hybrid nanocomposites containing intercalated DNA molecules, or co-intercalated mixtures of DNA and the redox protein, cytochrome c. Small-molecule reducing agents readily access the intercalated proteins. [source] Redox enzymes in the plant plasma membrane and their possible rolesPLANT CELL & ENVIRONMENT, Issue 12 2000A. 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] Direct Electrochemistry of Cytochrome,c at Modified Si(100) ElectrodesCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2010Simone Ciampi Abstract This paper demonstrates the direct electron transfer between the heme moiety of horse hearth cytochrome,c and a pyridinyl group on self-assembled-monolayer-modified Si(100) electrodes. Self-assembled monolayers (SAMs) containing the putative receptor ligand were prepared by a step-wise procedure using "click" reactions of acetylene-terminated alkyl monolayers and isonicotinic acid azide derivatives. Unoxidized Si(100) electrodes, possessing either isonicotinate or isonicotinamide receptor ligands, were characterized using X-ray photoelectron spectroscopy, contact-angle goniometry, cyclic voltammetry, and electrochemical impedance spectroscopy. The ability of isonicotinic acid terminated layers to coordinatively bind the redox center of cytochrome,c was found to be restricted to pyridinyl assemblies with a para -ester linkage present. The protocol detailed here offers an experimentally simple modular approach to producing chemically well-defined SAMs on silicon surfaces for direct electrochemistry of a well-studied model redox protein. [source] Transient complexes of redox proteins: structural and dynamic details from NMR studiesJOURNAL OF MOLECULAR RECOGNITION, Issue 6 2004Miguel Prudêncio Abstract Redox proteins participate in many metabolic routes, in particular those related to energy conversion. Protein,protein complexes of redox proteins are characterized by a weak affinity and a short lifetime. Two-dimensional NMR spectroscopy has been applied to many redox protein complexes, providing a wealth of information about the process of complex formation, the nature of the interface and the dynamic properties of the complex. These studies have shown that some complexes are non-specific and exist as a dynamic ensemble of orientations while in other complexes the proteins assume a single orientation. The binding interface in these complexes consists of a small hydrophobic patch for specificity, surrounded by polar, uncharged residues that may enhance dissociation, and, in most complexes, a ring or patch of charged residues that enhances the association by electrostatic interactions. The entry and exit port of the electrons is located within the hydrophobic interaction site, ensuring rapid electron transfer from one redox centre to the next. Copyright © 2004 John Wiley & Sons, Ltd. [source] Reactive oxygen species and antioxidants in legume nodulesPHYSIOLOGIA PLANTARUM, Issue 4 2000Manuel Becana Reactive oxygen species are a ubiquitous danger for aerobic organisms. This risk is especially elevated in legume root nodules due to the strongly reducing conditions, the high rates of respiration, the tendency of leghemoglobin to autoxidize, the abundance of nonprotein Fe and the presence of several redox proteins that leak electrons to O2. Consequently, nodules are particularly rich in both quantity and diversity of antioxidant defenses. These include enzymes such as superoxide dismutase (EC 1.15.1.1) and ascorbate peroxidase (EC 1.11.1.11) and metabolites such as ascorbate and thiol tripeptides. Nodule antioxidants have been the subject of intensive molecular, biochemical and functional studies that are reviewed here. The emerging theme is that antioxidants are especially critical for the protection and optimal functioning of N2 fixation. We hypothesize that this protection occurs at least at two levels: the O2 diffusion barrier in the nodule parenchyma (inner cortex) and the infected cells in the central zone. [source] Redox enzymes in the plant plasma membrane and their possible rolesPLANT CELL & ENVIRONMENT, Issue 12 2000A. 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] CxxS: Fold-independent redox motif revealed by genome-wide searches for thiol/disulfide oxidoreductase functionPROTEIN SCIENCE, Issue 10 2002Dmitri E. Fomenko Abstract Redox reactions involving thiol groups in proteins are major participants in cellular redox regulation and antioxidant defense. Although mechanistically similar, thiol-dependent redox processes are catalyzed by structurally distinct families of enzymes, which are difficult to identify by available protein function prediction programs. Herein, we identified a functional motif, CxxS (cysteine separated from serine by two other residues), that was often conserved in redox enzymes, but rarely in other proteins. Analyses of complete Escherichia coli, Campylobacter jejuni, Methanococcus jannaschii, and Saccharomyces cerevisiae genomes revealed a high proportion of proteins known to use the CxxS motif for redox function. This allowed us to make predictions in regard to redox function and identity of redox groups for several proteins whose function previously was not known. Many proteins containing the CxxS motif had a thioredoxin fold, but other structural folds were also present, and CxxS was often located in these proteins upstream of an ,-helix. Thus, a conserved CxxS sequence followed by an ,-helix is typically indicative of a redox function and corresponds to thiol-dependent redox sites in proteins. The data also indicate a general approach of genome-wide identification of redox proteins by searching for simple conserved motifs within secondary structure patterns. [source] Towards structural studies of the old yellow enzyme homologue SYE4 from Shewanella oneidensis and its complexes at atomic resolutionACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 1 2010Jonathan Elegheert Shewanella oneidensis is an environmentally versatile Gram-negative ,-proteobacterium that is endowed with an unusually large proteome of redox proteins. Of the four old yellow enzyme (OYE) homologues found in S. oneidensis, SYE4 is the homologue most implicated in resistance to oxidative stress. SYE4 was recombinantly expressed in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. The crystals belonged to the orthorhombic space group P212121 and were moderately pseudo-merohedrally twinned, emulating a P422 metric symmetry. The native crystals of SYE4 were of exceptional diffraction quality and provided complete data to 1.10,Å resolution using synchrotron radiation, while crystals of the reduced enzyme and of the enzyme in complex with a wide range of ligands typically led to high-quality complete data sets to 1.30,1.60,Å resolution, thus providing a rare opportunity to dissect the structure,function relationships of a good-sized enzyme (40,kDa) at true atomic resolution. Here, the attainment of a number of experimental milestones in the crystallographic studies of SYE4 and its complexes are reported, including isolation of the elusive hydride,Meisenheimer complex. [source] Structure of the twin-arginine signal-binding protein DmsD from Escherichia coliACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2009Suresh Kumar Ramasamy The translocation of folded proteins via the twin-arginine translocation (Tat) pathway is regulated to prevent the futile export of inactive substrate. DmsD is part of a class of cytoplasmic chaperones that play a role in preventing certain redox proteins from premature transport. DmsD from Escherichia coli has been crystallized in space group P41212, with unit-cell parameters a = b = 97.45, c = 210.04,Å, in the presence of a small peptide. The structure has been solved by molecular replacement to a resolution of 2.4,Å and refined to an R factor of 19.4%. There are four molecules in the asymmetric unit that may mimic a higher order structure in vivo. There appears to be density for the peptide in a predicted binding pocket, which lends support to its role as the signal-recognition surface for this class of proteins. [source] Electrochemical Quartz Crystal Microbalance Studies on Enzymatic Specific Activity and Direct Electrochemistry of Immobilized Glucose Oxidase in the Presence of Sodium Dodecyl Benzene Sulfonate and Multiwalled Carbon NanotubesBIOTECHNOLOGY PROGRESS, Issue 1 2008Yuhua Su The electrochemical quartz crystal microbalance (EQCM) technique was utilized to monitor in situ the adsorption of glucose oxidase (GOD) and the mixture of GOD and sodium dodecyl benzene sulfonate (SDBS) onto Au electrodes with and without modification of multiwalled carbon nanotubes (MWCNTs) or SDBS/MWCNTs composite, and the relationship between enzymatic specific activity (ESA) and direct electrochemistry of the immobilized GOD was quantitatively evaluated for the first time. Compared with the bare gold electrode at which a little GOD was adsorbed and the direct electrochemistry of the adsorbed GOD was negligible, the amount and electroactivity of adsorbed GOD were greatly enhanced when the GOD was mixed with SDBS and then adsorbed onto the SDBS/MWCNTs modified Au electrode. However, the ESA of the adsorbed GOD was fiercely decreased to only 16.1% of the value obtained on the bare gold electrode, and the portion of adsorbed GOD showing electrochemical activity exhibited very low enzymatic activity, demonstrating that the electroactivity and ESA of immobilized GOD responded oppositely to the presence of MWCNTs and SDBS. The ESA results obtained from the EQCM method were well supported by conventional UV-vis spectrophotometry. The direct electrochemistry of redox proteins including enzymes as a function of their biological activities is an important concern in biotechnology, and this work may have presented a new and useful protocol to quantitatively evaluate both the electroactivity and ESA of trace immobilized enzymes, which is expected to find wider applications in biocatalysis and biosensing fields. [source] Redox proteins in mammalian cell death: an evolutionarily conserved function in mitochondria and prokaryotesCELLULAR MICROBIOLOGY, Issue 4 2003Vasu Punj Summary Mammalian cell mitochondria are believed to have prokaryotic ancestry. Mitochondria are not only the powerhouse of energy generation within the eukaryotic cell but they also play a major role in inducing apoptotic cell death through release of redox proteins such as cytochrome c and the apoptosis-inducing factor (AIF), a flavoprotein with NADH oxidase activity. Recent evidence indicates that some present day prokaryotes release redox proteins that induce apoptosis in mammalian cells through stabilization of the tumour suppressor protein p53. p53 interacts with mitochondria either directly or through activation of the genes for pro-apoptotic proteins such as Bax or NOXA or genes that encode redox enzymes responsible for the production of reactive oxygen species (ROS). The analogy between the ancient ancestors of present day bacteria, the mitochondria, and the present day bacteria with regard to their ability to release redox proteins for triggering mammalian cell death is an interesting example of functional conservation during the hundreds of millions of years of evolution. It is possible that the ancestors of the present day prokaryotes released redox proteins to kill the ancestors of the eukaryotes. During evolution of the mitochondria from prokaryotes as obligate endosymbionts, the mitochondria maintained the same functions to programme their own host cell death. [source] | |||||||||||||