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We have applied the technique of distance estimations using the exogenous paramagnetic probe dysprosium (III) complexed with EDTA (DyEDTA) to study the topology of Escherichia coli dimethyl sulfoxide reductase (DmsABC) in situ in cytoplasmic membrane and whole cell preparations. The electron transfer subunit (DmsB) of this enzyme contains four [4Fe-4S](More)
We have examined the role of the quinone-binding (Q(P)) site of Escherichia coli succinate:ubiquinone oxidoreductase (succinate dehydrogenase) in heme reduction and reoxidation during enzyme turnover. The SdhCDAB electron transfer pathway leads from a cytosolically localized flavin adenine dinucleotide cofactor to a Q(P) site located within the(More)
Proinflammatory cytokines depress myocardial contractile function by enhancing the expression of inducible NO synthase (iNOS), yet the mechanism of iNOS-mediated myocardial injury is not clear. As the reaction of NO with superoxide to form peroxynitrite markedly enhances the toxicity of NO, we hypothesized that peroxynitrite itself is responsible for(More)
We have used site-directed mutagenesis to alter the [Fe-S] cluster composition of Escherichia coli dimethyl sulfoxide (DMSO) reductase (DmsABC). The electron-transfer subunit (DmsB) of this enzyme contains 16 Cys residues arranged in 4 groups (I-IV) which provide ligands to 4 [4Fe-4S] clusters [Cammack, R., & Weiner, J. H. (1990) Biochemistry 29,(More)
We have identified the organic component of the molybdenum cofactor in Escherichia coli dimethyl sulfoxide reductase (DmsABC) to be molybdopterin (MPT) guanine dinucleotide (MGD) and have studied the effects of tungstate and a mob mutation on cofactor (Mo-MGD) insertion. Tungstate severely inhibits anaerobic growth of E. coli on a glycerol-dimethyl(More)
Under anaerobic conditions and in the presence of nitrate, the facultative anaerobe Escherichia coli synthesises an electron-transport chain comprising a primary dehydrogenase and the terminal membrane-bound nitrate reductase A (NarGHI). This review focuses on recent advances obtained on the structure and function of the three protein subunits of(More)
We have used fluorescence quench titrations, EPR spectroscopy and steady-state kinetics to study the effects of site-directed mutants of FrdB, FrdC and FrdD on the proximal menaquinol (MQH(2)) binding site (Q(P)) of Escherichia coli fumarate reductase (FrdABCD) in cytoplasmic membrane preparations. Fluorescence quench (FQ) titrations with the fluorophore(More)
The respiratory molybdoenzyme nitrate reductase (NarGHI) from Escherichia coli has been studied by protein film voltammetry, with the enzyme adsorbed on a rotating disk pyrolytic graphite edge (PGE) electrode. Catalytic voltammograms for nitrate reduction show a complex wave consisting of two components that vary with pH, nitrate concentration, and the(More)
We have studied the effect of a mobAB mutation and tungstate on molybdo-molybdopterin-guanine dinucleotide (Mo-MGD) insertion into Escherichia coli nitrate reductase (NarGHI). Preparation of fluorescent oxidized derivatives of MGD (Form A and Form B) indicates that in a mobAB mutant there is essentially no detectable cofactor present in either the(More)