Mechanism of sulfide-quinone reductase investigated using site-directed mutagenesis and sulfur analysis
Griesbeck C, Schütz M, Schödl T, Bathe S, Nausch L, Mederer N, Vielreicher M, Hauska G (2002)
Publication Type: Journal article
Publication year: 2002
Journal
Book Volume: 41
Pages Range: 11552-11565
Journal Issue: 39
DOI: 10.1021/bi026032b
Abstract
Biological sulfide oxidation is a reaction occurring in all three domains of life. One enzyme responsible for this reaction in many bacteria has been identified as sulfide:quinone oxidoreductase (SQR). The enzyme from Rhodobacter capsulatus is a peripherically membrane-bound flavoprotein with a molecular mass of approximately 48 kDa, presumably acting as a homodimer. In this work, SQR from Rb. capsulatus has been modified with an N-terminal His tag and heterologously expressed in and purified from Escherichia coli. Three cysteine residues have been shown to be essential for the reductive half-reaction by site-directed mutagenesis. The catalytic activity has been nearly completely abolished after mutation of each of the cysteines to serine. A decrease in fluorescence on reduction by sulfide as observed for the wild-type enzyme has not been observed for any of the mutated enzymes. Mutation of a conserved valine residue to aspartate within the third flavin-binding domain led to a drastically reduced substrate affinity, for both sulfide and quinone. Two conserved histidine residues have been mutated individually to alanine. Both of the resulting enzymes exhibited a shift in the pH dependence of the SQR reaction. Polysulfide has been identified as a primary reaction product using spectroscopic and chromatographic methods. On the basis of these data, reaction mechanisms for sulfide-dependent reduction and quinone-dependent oxidation of the enzyme and for the formation of polysulfide are proposed.
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APA:
Griesbeck, C., Schütz, M., Schödl, T., Bathe, S., Nausch, L., Mederer, N.,... Hauska, G. (2002). Mechanism of sulfide-quinone reductase investigated using site-directed mutagenesis and sulfur analysis. Biochemistry, 41(39), 11552-11565. https://dx.doi.org/10.1021/bi026032b
MLA:
Griesbeck, Christoph, et al. "Mechanism of sulfide-quinone reductase investigated using site-directed mutagenesis and sulfur analysis." Biochemistry 41.39 (2002): 11552-11565.
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