Griesbeck, Christoph and Schuetz, Michael and Schoedl, Thomas and Bathe, Stephan and Nausch, Lydia and Mederer, Nicola and Vielreicher, Martin and Hauska, Guenther (2002) Mechanism of sulfide-quinone reductase investigated using site-directed mutagenesis and sulfur analysis. BIOCHEMISTRY, 41 (39). pp. 11552-11565. ISSN 0006-2960
Full text not available from this repository. (Request a copy)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.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | PURPLE PHOTOTROPHIC BACTERIUM; RHODOBACTER-CAPSULATUS; CHROMATIUM-VINOSUM; ESCHERICHIA-COLI; LIPOAMIDE DEHYDROGENASE; FLAVOCYTOCHROMES-C; SEQUENCE-ANALYSIS; ELEMENTAL SULFUR; AQUIFEX AEOLICUS; RNA-POLYMERASE; |
| Subjects: | 500 Science > 570 Life sciences 500 Science > 580 Botanical sciences |
| Divisions: | Biology, Preclinical Medicine > Institut für Pflanzenwissenschaften > Lehrstuhl für Zellbiologie und Pflanzenphysiologie (Prof. Dr. Klaus Grasser) |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 27 Aug 2021 06:21 |
| Last Modified: | 27 Aug 2021 06:21 |
| URI: | https://pred.uni-regensburg.de/id/eprint/39801 |
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