Zhongwei Zhao

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Succinate dehydrogenase is an indispensable enzyme involved in the Krebs cycle as well as energy coupling in the mitochondria and certain prokaryotes. During catalysis, succinate oxidation is coupled to ubiquinone reduction by an electron transfer relay comprising a flavin adenine dinucleotide cofactor, three iron-sulfur clusters, and possibly a heme b556.(More)
The ferroxidase activity of human ferritin has previously been associated with a diiron site situated centrally within the four-helix bundle of H-type chains (HuHF). However, direct information about the site of Fe(II) binding has been lacking, and events between Fe(II) binding and its oxidation have not previously been studied. A sequential stopped-flow(More)
A new substrate analogue, (2R)-1,2-dipalmitoyloxypropanethiophospho-1-D-myo-inositol (DPsPI), has been used in a new, continuous assay for phosphatidylinositol-specific phospholipase C (PI-PLC). DPsPI is superior to other substrate analogs that have been used for assaying PI-PLC since it is synthesized as a pure diastereomer and maintains both acyl chains(More)
Escherichia coli succinate dehydrogenase (SdhCDAB) catalyzes the oxidation of succinate to fumarate in the Krebs cycle, and during turnover, it produces superoxide radicals. SdhCDAB is a good model system for the succinate dehydrogenase (Sdh) found in the mitochondrial respiratory chain (complex II), as the subunits are structural homologues. Although(More)
We have studied the transient kinetics of quinol-dependent heme reduction in Escherichia coli nitrate reductase A (NarGHI) by the menaquinol analogue menadiol using the stopped-flow method. Four kinetic phases are observed in the reduction of the hemes. A transient species, likely to be associated with a semiquinone radical anion, is observed with kinetics(More)
Iron uptake into the nonheme ferritin of Escherichia coli (EcFtnA) and its site-directed variants have been investigated by Mössbauer spectroscopy. EcFtnA, like recombinant human H chain ferritin (HuHF), oxidized Fe(II) at a dinuclear ferroxidase center situated at a central position within each subunit. As with HuHF, Mössbauer subspectra observed between 1(More)
The iron storage molecule, ferritin, consists of an iron core surrounded by a shell of 24 protein subunits, which, in mammals, are of two types, H and L. Prior to storage of iron as a hydrous ferric oxide within the protein shell, Fe(II) is catalytically oxidized at dinuclear centers within H chains. When 48 Fe(II) atoms/molecule were added to 1 microM(More)
The iron storage proteins, ferritins, are found in all organisms which use iron. Here iron storage processes in the Escherichia coli ferritin (EcFtnA) are compared with those in human H-type ferritin (HuHF). Both proteins contain dinuclear iron centres that enable the rapid oxidation of 2 Fe(II) by O2. The presence of a third iron binding site in EcFtnA,(More)
The mechanism of phosphatidylinositol-specific phospholipase C (PI-PLC) has been suggested to resemble that of ribonuclease A. The goal of this work is to rigorously evaluate the mechanism of PI-PLC from Bacillus thuringiensis by examining the functional and structural roles of His-32 and His-82, along with the two nearby residues Asp-274 and Asp-33 (which(More)
We have studied the effects of site-directed mutations in Escherichia coli nitrate reductase A (NarGHI) on heme reduction by a menaquinol analogue (menadiol) using the stopped-flow method. For NarGHI(H66Y) and NarGHI(H187Y), both lacking heme b(L) but having heme b(H), the heme reduction by menadiol is abolished. For NarGHI(H56R) and NarGHI(H205Y), both(More)
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