3SXI

Crystal structure of sulfide:quinone oxidoreductase Cys128Ala variant from Acidithiobacillus ferrooxidans complexed with decylubiquinone

Summary for 3SXI

• Entry DOI: 10.2210/pdb3sxi/pdb
• Related: 3KPG 3KPI 3KPK 3SX6 3SY4 3SYI 3SZ0 3SZC 3SZF
• Descriptor: Sulfide-quinone reductase, putative, FLAVIN-ADENINE DINUCLEOTIDE, DODECYL-BETA-D-MALTOSIDE, ... (7 entities in total)
• Functional Keywords: sulfide:quinone oxidoreductase, cys128ala variant, integral monotopic membrane protein, complex with sulfide, oxidoreductase
• Biological source: Acidithiobacillus ferrooxidans
• Cellular location: Membrane ; Peripheral membrane protein : B7JBP8
• Total number of polymer chains: 1
• Total formula weight: 49584.89

Authors

Cherney, M.M.,Zhang, Y.,James, M.N.G.,Weiner, J.H. (deposition date: 2011-07-14, release date: 2012-05-16, Last modification date: 2017-11-08)

Primary citation

Cherney, M.M.,Zhang, Y.,James, M.N.,Weiner, J.H.
Structure-activity characterization of sulfide:quinone oxidoreductase variants.
J.Struct.Biol., 178:319-328, 2012

PubMed Abstract: Sulfide:quinone oxidoreductase (SQR) is a peripheral membrane protein that catalyzes the oxidation of sulfide species to elemental sulfur. The enzymatic reaction proceeds in two steps. The electrons from sulfides are transferred first to the enzyme cofactor, FAD, which, in turn, passes them onto the quinone pool in the membrane. Several wild-type SQR structures have been reported recently. However, the enzymatic mechanism of SQR has not been fully delineated. In order to understand the role of the catalytically essential residues in the enzymatic mechanism of SQR we produced a number of variants of the conserved residues in the catalytic site including the cysteine triad of SQR from the acidophilic, chemolithotrophic bacterium Acidithiobacillus ferrooxidans. These were structurally characterized and their activities for each reaction step were determined. In addition, the crystal structures of the wild-type SQR with sodium selenide and gold(I) cyanide have been determined. Previously we proposed a mechanism for the reduction of sulfides to elemental sulfur involving nucleophilic attack of Cys356 on C(4A) atom of FAD. Here we also consider an alternative anionic radical mechanism by direct electron transfer from Cys356 to the isoalloxazine ring of FAD.

PubMed: 22542586
DOI: 10.1016/j.jsb.2012.04.007

Experimental method

X-RAY DIFFRACTION (2.1792 Å)