کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
8290060 1536338 2014 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Characterization of the kinetics and electron paramagnetic resonance spectroscopic properties of Acidithiobacillus ferrooxidans sulfide:quinone oxidoreductase (SQR)
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شیمی
پیش نمایش صفحه اول مقاله
Characterization of the kinetics and electron paramagnetic resonance spectroscopic properties of Acidithiobacillus ferrooxidans sulfide:quinone oxidoreductase (SQR)
چکیده انگلیسی
Acidithiobacillus ferrooxidans sulfide:quinone oxidoreductase (SQR) catalyzes the oxidation of sulfide to polysulfide chains or elemental sulfur coupled to quinone reduction via a non-covalent FAD cofactor. We investigated the role of the FAD using kinetics and EPR spectroscopy. The properties of the enzyme were compared with alanine and/or serine variants of conserved cysteine residues (Cys128, Cys160, Cys356) structurally close to the FAD cofactor and histidine residues (His132, His198) implicated in function. When the pre-steady state reduction of FAD was monitored, variants of Cys128 and His132 had similar rates to wild-type enzyme confirming they do not participate in the reductive half reaction whereas variants of Cys160, Cys356 and His198 had greatly reduced activity. Using steady state kinetics of Na2S-dependent decylubiquinone (DUQ) reduction we measured a kcat of 6.5 s−1 and a Km (Na2S) of 3.0 μM and a Km (DUQ) of 3.4 μM. Variants of Cys160, Cys356 and His198 had greatly diminished DUQ reduction activity whereas variants of Cys128 and His132 were less affected. A neutral flavin semiquinone was observed in the EPR spectrum of SQR reduced with Na2S which was enhanced in the Cys160Ala variant suggesting the presence of a Cys356-Sγ-S-C4A-FAD adduct. Potentiometric titrations of the FAD semiquinone revealed an Em of −139 ± 4 mV at pH 7.0.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Archives of Biochemistry and Biophysics - Volume 564, 15 December 2014, Pages 110-119
نویسندگان
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