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PubMed1999

Redox-dependent and redox-independent subcomponents of protein degradation in perfused myocardium.

The integration of proteolytic pathways with metabolism was investigated in perfused rat myocardium. After a 10-min incorporation period, the minute-to-minute release of [3H]leucine from myocardial proteins was measured in nonrecirculating effluent perfusate. The nontoxic pro-oxidant probe diamide (100 microM) or a supraphysiological concentration of the endogenous oxidative metabolite dehydroascorbic acid (200 microM) reversibly inhibited 75% of myocardial proteolysis consisting of several known subcomponents (redox dependent); however, 25% of proteolysis was diamide insensitive (redox independent). Decrease in extracellular glucose concentration from 10 to 0.1 mM strongly increased the potencies of minimally effective concentrations of diamide (10 microM) or dehydroascorbic acid (15 microM) by approximately 10-fold to the respective potencies maximally inhibiting proteolysis. The reversal of diamide action was also strongly dependent on the perfusate glucose concentration observed at 0.1, 0.2, 1.0 and 10 mM glucose. Proteolytic inhibition caused by diamide (100 microM) was not accompanied by change in basal tissue ATP content of 5 micromol/g wet wt. Conversely, nearly lethal 60% ATP depletion caused by sodium azide (0.4 mM) was not accompanied by change in total [3H]leucine release. Results indicate that a large proteolytic subcomponent (75%) is maintained by redox chains fed by glucose; however, there is no apparent linkage of this proteolysis to short-term ATP fluctuations. A distinct major proteolytic subcomponent (25%) does not vary in response to experimental intervention in either ATP content or redox chains.

Adenosine Triphosphate↗
PubMed2005

Growth inhibition of drug-resistant species of Plasmodium falciparum by domain structured N1,N2-derivatized hydrazines: denticity effects, redox switches, and reductant-driven redox-cycling.

Six analogs of bidentate 1-[pyridoxylidene]-2-phenyl]hydrazine, twelve analogs of N2O-tridentate 1-[pyridoxylidene]-2-[heteroaryl]hydrazine, and four O2N-tridentate analogs of 1-[pyridoxylidene]-2-[heteroaroyl] hydrazines were synthesized and characterized. Their solutions in water and DMSO were assayed in vitro for activity against a chloroquine-resistant species of P. falciparum obtained from Hadassah Hospital Blood Bank in Jerusalem. The O2N-tridentate group was essentially inactive, whereas the bidentate group, with N and O liganding atoms, exhibited slight activity against late-stage trophozoites and schizonts of P. falciparum. The N2O-tridentate group, by contrast, was remarkably active against resistant P. falciparum, highlighting the importance of the Denticity Effect in this system. It is assumed that the pyridoxal-based chelator acts as an iron redox mediator, controlling the first coordination sphere and, therefore, the immediate chemical environment of the iron. Chelation of iron-(II) presumably facilitates its oxidation..The Fe(II) --> Fe(III) intra-electron transfer, may be viewed as a switch ("redox switch"), controlling the thermodynamic stability and kinetic lability of the coordination shell. The redox-switch is accompanied by the appearance of a carbon-based Fe-(III)-chelate radical, capable of donating its free electron to the parasite-DNA, thus causing death. The antimalarial N2O-tridentate Fe(III)-chelates appear to be prone to redox-switch, and tend to be converted into their Fe(II) species, whereas the inactive O2N-tridentate analogs apparently cannot do so.

Animals↗
PubMed1988

Direct electrochemical probes of redox protein and redox enzyme structure and function.

The direct electrochemistry of redox proteins has been achieved at a variety of electrodes, including modified gold and pyrolytic graphite. Careful design of electrode surfaces and electrolyte conditions are required for the attainment of rapid and reversible protein-electrode interaction. Protein-protein complexes can be studied by using selective electrode surfaces. The "well-behaved" electrochemistry of redox proteins can be exploited by coupling the electrode reaction to enzymes for which the redox proteins act as cofactors. The electron-transfer reactions of more complex systems, such as redox enzymes, are now being examined.

Cytochromes↗
PubMed2006

Characterization and redox properties of cytochrome c552 from Thermus thermophilus adsorbed on different self-assembled thiol monolayers, used to model the chemical environment of the redox partner.

The structure of cytochrome c552 (Cyt-c552) from Thermus thermophilus shows many differences to other c-type cytochromes. The rich lysine domain close to the heme does not exist in this cytochrome, allowing us to postulate that the interaction with its redox partner must be different to the cytochrome c/cytochrome c oxidase interaction. We report a study of Cyt-c552 adsorbed on self-assembled monolayers (SAMs) of functionalized alkanethiols used to mimic the chemical properties of its redox partner (ba3-oxydase). Hydrophilic (-COOH), polar (-OH), hydrophobic (-CH3), and mixed (-OH/-CH3) SAMs grafted on roughened silver electrodes were characterized by X-ray photoelectron spectroscopy. Surface enhanced resonance Raman spectroscopy (SERRS) was employed to determine the structure and the redox properties (E degrees and number of transferred electron) of the heme of Cyt-c552 adsorbed on roughened silver electrodes coated by the different SAMs. The surface that most closely models the environment of the ba3-oxidase is a mixed SAM formed by 50% polar [Ag-(CH2)5-CH2OH] and 50% hydrophobic [Ag-(CH2)5-CH3] alkanethiols. Only the native form B1(6cLS) of Cyt-c552 is detected by SERRS when the protein is adsorbed on such a surface that promotes a protein orientation favorable for the electron transfer (number of transferred electron = 1). We shall discuss the differences and similarities of the electron-transfer mechanism of Cyt-c552 compared to cyt-c.

Adsorption↗
PubMed2003

Could redox-switched binding of a redox-active ligand to a copper(II) centre drive a conformational proton pump gate? A synthetic model study.

A proposal for a redox-linked conformational gate to proton translocation--a proton pump gate--based upon a transition-metal redox-switchable hemilabile ligand (RHL) system is made. Consideration of the requirements for such a system reveals copper(II) to be the ideal metal centre. To test the proposal and, thereby, to provide an artificial proton pump gate, the copper coordination chemistry of three tris(pyridylmethyl)amine (tpa) ligands with one "leg" (PY*) substituted at the 6-position of the pyridine ring by a dimethoxyphenyl (L(1)), a hydroquinone (H(2)L(2)) or a quinone (L(3)) substituent has been investigated. Crystal structures of sp-[Cu(kappa(4)N-L(1))Cl]Cl.3 H(2)O (sp=square pyramidal), sp-[Cu(kappa(3)N-H(2)L(2))Cl(2)] and tbp-[Cu(kappa(4)N,kappaO-HL(2))][PF(6)] (tbp=trigonal bipyramidal) have been determined. The Cu(I) complexes [Cu(L)(MeCN)(n)](+) (L=L(1), H(2)L(2)) display physicochemical properties consistent with a "dangling" PY* leg; from the NMR spectra, the barriers to inversion of the ligand amine donor for the Cu(I) complexes are estimated to be within the range of about 30-45 kJ mol(-1). In the Cu(II) complexes, coordination of the PY* leg is finely balanced and critically depends on the nature of the PY* substituent and the availability of potential co-ligand(s). For example, tbp-[Cu(kappa(4)N-L(1))Cl](+) reacts cleanly with Cl(-) ions to afford sp-[Cu(kappa(3)N-L(1))Cl(2)]; Vis/NIR spectrophotometric titrations suggest the affinity of tbp-[Cu(kappa(4)N-L(1))Cl](+) for Cl(-) ion in dichloromethane is 9.7 x 10(2) and is at least 10(4)-fold greater than that of tbp-[Cu(kappa(4)N-L(3))Cl](+). The complex sp-[Cu(kappa(3)N-H(2)L(2))Cl(2)] has a "dangling" PY* leg, in which an intramolecular OH(hydroquinone).N(pyridine) hydrogen bond "ties-up" the pyridyl nitrogen atom, and reacts with Brønsted bases to give tbp-[Cu(kappa(4)N,kappaO-HL(2))](+). Two-electron oxidation of sp-[Cu(kappa(3)N-H(2)L(2))Cl(2)] is linked to loss of two protons and a conformational change, and affords tbp-[Cu(kappa(4)N-L(3))Cl](+). The [Cu(kappa(3)N-H(2)L(2))Cl(2)]-[Cu(kappa(4)N-L(3))Cl](+) system provides a first demonstration of the critical step in the proposed proton pumping cycle, namely a redox-driven and proton-linked conformational change. The possible biological relevance of this work to proton pumping in cytochrome c oxidase is mentioned.

Copper↗
PubMed1993

Amino acid sequence of a high redox potential ferredoxin (HiPIP) from the purple phototrophic bacterium Rhodopila globiformis, which has the highest known redox potential of its class.

Rhodopila globiformis HiPIP has a redox potential (ca. 450 mV) that is 100 mV higher than any other known iron-sulfur protein. The amino acid sequence contains 57 residues and can be aligned with that of Thiobacillus ferrooxidans without any insertions or deletions and is 51% identical. Rp. globiformis HiPIP is also similar to that of Rhodocyclus tenuis, but six- and two-residue gaps must be postulated and there is only 37% identity. Most of the amino acid residues near the iron-sulfur cluster are similar in these two species based on inspection of the three-dimensional structure of Rc. tenuis HiPIP. The reason for the higher redox potential may be a more hydrophilic environment of the Rp. globiformis HiPIP iron-sulfur cluster due to the above two deletions and to substitution of Ser 32 for Gly. Rp. globiformis is unusual in that it has a cytochrome c2 in addition to the HiPIP, and it too has a very high redox potential. These results suggest that the cytochrome c2 and HiPIP may function interchangeably and that the species normally resides in a very high potential environment, although it is not known to grow aerobically in the dark.

Amino Acid Sequence↗
PubMed1994

Role of zinc-coordination and of the glutathione redox couple in the redox susceptibility of human transcription factor Sp1.

We show that thiol-groups confer redox-susceptibility to the zinc-finger transcription factor Sp1 and that this redox-susceptibility is prevented by DNA-binding and depends on zinc-coordination of the protein. Apo-Sp1 contained in metal depleted nuclear extracts of human K562 cells exhibited a markedly increased susceptibility towards oxidizing and alkylating agents, as compared to holo-Sp 1. Moreover, DNA binding of apo-Sp1, but not of the holo-protein, was dramatically decreased in the presence of GSH/GSSG ratios within the physiological range. We compared these results with the redox behaviour of two other transcription factors, OTF-1 and NF1, which was found to be different in several aspects from that of Sp1.

Apoproteins↗
PubMed1996

The interaction of antitumor-active anthraquinones with biologically important redox couples: I. Spectrophotometric investigation of the interaction of carminic acid and mitoxantrone with the iron (II, III) and copper (I, II) redox couples.

Studying the interaction of antitumor-active anthraquinones with biologically important redox couples is important in understanding the possible reductive or oxidative mode of metabolism of these antineoplastic agents coupled with the formation of free radicals. The interactions of such anthraquinones, i.e., carminic acid (CA) and mitoxantrone (Mx) with iron(II, III) and copper(I, II) redox couples in oxygenated and deaerated solutions, were investigated by UV-Visible and IR-spectroscopy. The superoxide radical reagent, nitroblue tetrazolium (NBT), was added to the metal and anthraquinone solutions and their binary mixtures at varying pH. Formazan, the reduction product of NBT, was produced mainly as a result of Fe(II)-NBT and Fe(II)-Mx-NBT interactions. The ternary mixtures of the lower valencies of iron and copper with CA and NBT exhibited intensive charge-transfer bands in the visible region, while metal-Mx-NBT combinations did not produce such bands, possibly due to the blockage of the redox-active aminoethanolamine side-chains of Mx through coordination with the metals. Copper-Mx combinations showed an oxygen sensitivity as spectral evidence was obtained for the oxidative transformation of Mx to the cyclic primary metabolite. The results were evaluated in regard to the possible oxidative activation of the studied anthracenediones with iron and copper systems.

Anthraquinones↗
PubMed2006

Computation of the redox and protonation properties of quinones: towards the prediction of redox cycling natural products.

Quinone metabolites perform a variety of key functions in plants, including pathogen protection, oxidative phosphorylation, and redox signaling. Many of these structurally diverse compounds have been shown to exhibit potent antimicrobial, anticancer, and anti-inflammatory properties, although the exact mechanisms of action are far from understood. Redox cycling has been proposed as a possible mechanism of action for many quinone species. Experimental determination of the essential thermodynamic data (i.e. electrochemical and pKa values) required to predict the propensity towards redox cycling is often difficult or impossible to obtain due to experimental limitations. We demonstrate a practical computational approach to obtain reasonable estimates of these parameters.

Biological Products↗
PubMed2002

Redox regulation of cytosolic glycerol-3-phosphate dehydrogenase: Cys(102) is the target of the redox control and essential for the catalytic activity.

Cytosolic glycerol-3-phosphate dehydrogenase (cG3PDH) occupies the branch point between the glycolytic pathway and triglyceride biosynthesis. However, the regulatory mechanism of the cG3PDH activity has remained obscure. Here we report that cG3PDH is efficiently inhibited by modification of the thiol group through a redox mechanism. In this study, we found that sodium selenite and nitric oxide (NO) donors such as S-nitroso-N-acetylpenicillamine and 3-morpholinosydnonimine inhibited cG3PDH activity, and that similar effects could be achieved with selenium metabolites such as selenocysteine and selenomethionine. Furthermore, we found that reducing agents, such as dithiothreitol and beta-mercaptoethanol, restored the cG3PDH activity suppressed by selenite and NO both in vitro and in cultured cells. Buthionine sulfoximine depleted levels of both reduced glutathione and the oxidized form but had no effect on the suppression of cG3PDH activity by selenite in cultured cells. Moreover, thiol-reactive agents, such as N-ethylmaleimide and o-iodosobenzoic acid, blocked the enzyme activity of cG3PDH through the modification of redox-sensitive cysteine residues in cG3PDH. The inhibitor of NO synthase, L-N(G)-nitro-arginine, restored the cG3PDH activity inhibited by NO in cultured cells, whereas the inhibitor of guanylyl cyclase, 1H-[1,2,4] oxadiazole[4,3-alpha] quinoxalin-1-one (ODQ), has no effect. NO directly inhibits cG3PDH activity not via a cGMP-dependent mechanism. Finally, using site-directed mutagenesis, we found that Cys(102) of cG3PDH was sensitive to both selenite and NO. From the results, we suggest that cG3PDH is a target of cellular redox regulation.

Animals↗
PubMed2002

Felbamate-induced apoptosis of hematopoietic cells is mediated by redox-sensitive and redox-independent pathways.

Felbamate (FBM; 2-phenyl-1,3-propanediol dicarbamate) is an approved antiepileptic drug shown to be effective in a variety of seizure disorders refractory to other treatments. However, its use has been restricted because of association with occurrence of rare cases of aplastic anemia and hepatic failure. Since it was shown that FBM metabolism requires glutathione (GSH), we used two experimental protocols to determine if the effects of specific metabolites were sensitive to redox pathways. FBM and its metabolite W873 (2-phenyl-1,3-propanediol monocarbamate), at 0.1 mg/ml, induced increased apoptosis of bone marrow cells from B10.AKM mice as compared with B10.BR mice. Study of the effects of the drug on human promonocytic cell line U937 cells showed that FBM and the metabolite W2986 [2-(4-hydroxyphenyl)-1,3 propanediol dicarbamate], at higher concentrations (0.5 mg/ml), induced apoptosis in this cell line. We also observed that while FBM and its metabolites induced increased apoptosis of B cells with reduced intracellular GSH levels, addition of exogenous GSH decreased apoptosis induced by W873 but did not significantly affect apoptosis induced by FBM or W2986. Our results suggest that, at concentrations used during the present investigations, FBM metabolites induce apoptosis via redox-sensitive and redox-independent pathways.

Animals↗
PubMed2001

Amount and redox state of cytoplasmic, membrane and periplasmic proteins in Escherichia coli redox mutants.

We analyzed the amount and redox state of cytoplasmic, membrane and periplasmic proteins in Escherichia coli mutants deficient in thioredoxin, thioredoxin reductase, glutathione and DsbA, by observing the electrophoretic profile of bacterial extracts after in vivo labelling with monobromobimane. Our results show that these mutations affected not only the amount and the redox state of proteins localized in the same compartment as the deficient oxidoreductase, but also those of the proteins localized in other compartments. These results concord with the hypothesis that there is a link between the redox reactions that occur in the cytoplasm and the periplasm.

Bacterial Proteins↗
PubMed1995

Polyacrylamide-based redox polymer for connecting redox centers of enzymes to electrodes.

Enzyme electrodes based on complexing a water-soluble copolymer of acrylamide and vinylimidazole with [Os(dmebpy)2C1]+/2+ (dmebpy = 4,4'-dimethyl-2,2'-bipyridine) and cross-linking with oxidases by water-soluble cross-linkers are described. The potential of the polyacrylamide-based redox polymer is +55 mV (SCE), a typical electron diffusion coefficient (De) in the redox hydrogel that results from its cross-linking is (1.3 +/- 0.1) x 10(-9) cm2/s. The properties of the enzyme electrodes formed when this redox hydrogel "wired" horseradish peroxidase (HRP), lactate oxidase (LOx) or glucose oxidase (GOx) depended on the thickness of the hydrogel film, the chemistry of their cross-linking, and their enzyme content. At the wired HRP electrodes, H2O2 was electrocatalytically reduced to water at 0.0 V (SCE). Lactate and glucose were electrocatalytically oxidized at 0.16 V (SCE). The GOx electrodes, when made with 140 micrograms/cm2 thick polymer films, were selective for glucose in the presence of physiological concentrations of urate and ascorbate.

Acrylic Resins↗
PubMed1995

Participation of the disulfide bridge in the redox cycle of the ferredoxin from the hyperthermophile Pyrococcus furiosus: 1H nuclear magnetic resonance time resolution of the four redox states at ambient temperature.

The oxidized and reduced forms of the [4Fe-4S]-containing ferredoxin from the hyperthermophilic archaeon Pyrococcus furiosus, Pf, have been investigated by 1H nuclear magnetic resonance spectroscopy, electron paramagnetic resonance spectroscopy and thiol titrations. We have identified and isolated at Ambient temperature four distinct redox states for the [4Fe-4S] form of the ferredoxin. These states differ in the redox state of the cluster, which is coordinated by Cys 11, Asp 14, Cys 17, and Cys 56, and of a disulfide bridge between Cys 21 and Cys 48. The protein, as isolated under anaerobic conditions, designated 4Fe FdBred, contains the reduced cluster and two free thiols. The cluster, but not the thiols, is readily oxidized by brief exposure to O2 to yield 4Fe FdBOX. Prolonged O2 treatment (> 24 h at 30 degrees C) is required to generate the protein with a disulfide (4Fe FdAOX) while this fully oxidized form is readily converted by brief reduction with sodium dithionite to the protein with a reduced cluster and a disulfide (4Fe FdAred). Analyses of the magnitude and the number of hyperfine-shifted resonances in each of the four redox states are discussed.

Archaea↗
PubMed1985

Kinetics of reduction of high redox potential ferredoxins by the semiquinones of Clostridium pasteurianum flavodoxin and exogenous flavin mononucleotide. Electrostatic and redox potential effects.

We have measured the ionic strength dependence of the rate constants for the electron-transfer reactions of flavin mononucleotide (FMN) and flavodoxin semiquinones with 10 high redox potential ferredoxins (HiPIP's). The rate constants were extrapolated to infinite ionic strength by using a theoretical model of electrostatic interactions developed in our laboratory. In all cases, the sign of the electrostatic interaction was the same as the protein net charge, but the magnitudes were much smaller. The results are consistent with a model in which the electrical charges are approximately uniformly distributed over the HiPIP surface and in which there are both short- and long-range electrostatic interactions. An electrostatic field calculation for Chromatium vinosum HiPIP is consistent with this. The presumed site of electron transfer includes that region of the protein surface to which the iron-sulfur cluster is nearest and appears to be relatively hydrophobic. The principal short-range electrostatic interaction would involve the negative charge on the iron-sulfur cluster. For some net negatively charged proteins, this effect is magnified, and for net positively charged HiPIP's, it is counterbalanced. The rate constants extrapolated to infinite ionic strength can be correlated with redox potential differences between the reactants, as has previously been shown for cytochrome-flavin semiquinone reactions. Both electrostatic and redox potential effects are magnified for the flavodoxin semiquinone as compared to the FMN semiquinone-HiPIP reactions. This was also observed previously for the flavin semiquinone-cytochrome reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzoquinones↗
PubMed1997

Regulation of oxidation-reduction potentials through redox-linked ionization in the Y98H mutant of the Desulfovibrio vulgaris [Hildenborough] flavodoxin: direct proton nuclear magnetic resonance spectroscopic evidence for the redox-dependent shift in the pKa of Histidine-98.

Flavodoxin from Desulfovibrio vulgaris is a low molecular weight (15 000 Da) acidic flavoprotein that contains a single flavin mononucleotide (FMN) cofactor. A distinguishing feature of the flavodoxin family is the exceptionally low midpoint potential of the semiquinone/hydroquinone couple. Tyrosine-98, which flanks the outer or si face of the FMN, plays an important role in establishing the oxidation-reduction properties of the bound cofactor as demonstrated by the substitution of a number of amino acids at this position [Swenson, R. P., & Krey, G. D. (1994) Biochemistry 33, 8505-8514]. The midpoint potential for the semiquinone/hydroquinone couple increases substantially when basic residues are introduced at this position. The pH dependency in the Y98H mutant is consistent with a redox-linked ionization model in which the favorable electrostatic coupling between the imidazolium cation and the flavin hydroquinone anion is responsible for the higher potential. Such a model predicts an increase in the pKa of 1.5 units for His98 upon complete reduction of the FMN. In this study, proton nuclear magnetic resonance spectroscopy was used to directly determine the intrinsic pKa of His98 as a function of the redox state of the cofactor in this flavodoxin. Values for the pKa of His98 in the oxidized and fully reduced flavodoxin are 7.02 +/- 0.08 and 8.43 +/- 0.11, respectively, an increase in the pKa by 1.41 units, which conforms with the previous prediction. These results provide direct experimental proof of the redox-linked ionization of this residue and provides further evidence of the crucial role of electrostatic interactions, in this case, in the stabilization of the flavin hydroquinone anion. This phenomenon may represent a general mechanism in the modulation of the reduction potential of the flavin cofactor within flavoenzymes in which ionizable groups such as histidine in the active center change ionization states during the catalytic cycle.

Binding Sites↗
PubMed2006

Redox chemistry of the acetato-bridged clusters [M3(mu3-O)n(mu-O2CCH3)6(H2O)3]2+ (M = Mo, W, n = 1, 2): reversible redox between mono-micro3-oxo d8 M(III)2M(IV) and d9 M(III)3 forms.

A cyclic voltammogram of aqueous 0.1 mol dm(-3) triflic acid solutions of the d6 bioxo-capped M-M bonded cluster [Mo3(mu3-O)2(O2CCH3)6(H2O)3]2+ at a glassy carbon electrode at 25 degrees C gives rise to an irreversible 3e- cathodic wave to a d9 Mo(III)3 species at -0.8 V vs. SCE which on the return scan gives rise to two anodic waves at +0.05 V vs. SCE (E(1/2), 1e- reversible to d8 Mo(III)2Mo(IV)) and +0.48 V vs. SCE (2e- irreversible back to d6 Mo(IV)3). The number of electrons passed at each redox wave has been confirmed by redox titration and controlled potential electrolysis which resulted in 90% recovery of [Mo3(mu3-O)2(O2CCH3)6(H2O)3]2+ following electrochemical re-oxidation at +0.8 V. A corresponding CV study of the d8 monoxo-capped W(III)2W(IV) cluster [W3(mu3-O)(O2CCH3)6(H2O)3]2+ gives rise to a reversible 1e- cathodic process at -0.92 V vs. SCE to give the d9 W(III)3 species [W3(mu3-O)(O2CCH3)6(H2O)3]+; the first authentic example of a W(III) complex with coordinated water ligands. However the cluster is too unstable (O2/water sensitive) to allow isolation. Comparisons with the cv study on [Mo3(mu3-O)2(O2CCH3)6(H2O)3]2+ suggest irreversible reduction of this complex to monoxo-capped [Mo(III)3(mu3-O)(O2CCH3)6(H2O)3]+ followed by reversible oxidation to its d8 counterpart [Mo3(mu3-O)(O2CCH3)6(H2O)3]2+ (Mo(III)2Mo(IV)) and finally irreversible oxidation back to the starting bioxo-capped cluster. Exposing the d9 Mo(III)3 cluster to air (O2) however gives a different final product with evidence of break up of the acetate bridged framework. Corresponding redox processes on d6 [W3(mu3-O)2(O2CCH3)6(H2O)3]2+ are too cathodic to allow similar generation of the monoxo-capped W(III)3 and W(III)2W(IV) clusters at the electrode surface.

Journal Article↗
PubMed2000

Skeletal muscle ryanodine receptor is a redox sensor with a well defined redox potential that is sensitive to channel modulators.

Hyperreactive sulfhydryl groups associated with the Ca(2+) release protein from sarcoplasmic reticulum are shown to have a well defined reduction potential that is sensitive to the cellular environment. Ca(2+) channel activators lower the redox potential of the ryanodine receptor, which favors the oxidation of thiols and the opening of the Ca(2+) release protein. In contrast, channel inhibitors increase the redox potential, which favors the reduction of disulfides and the closure of the release protein. Modulation of redox potential of reactive thiols may be a general control mechanism by which sarcoplasmic/endoplasmic reticulum, ryanodine receptors/IP(3) receptors, control cytoplasmic Ca(2+) concentrations.

Animals↗