3mm5

Dissimilatory sulfite reductase in complex with the substrate sulfite

spinqualitylabelsall models 3mm5, resolution 1.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3mm5 is a 4 chain structure with sequence from Archaeoglobus fulgidus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.8Å Ligands: SO3, SRM Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function DSRA_ARCFU Catalyzes the reduction of sulfite to sulfide. This is the terminal oxidation reaction in sulfate respiration. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed A vital process in the biogeochemical sulfur cycle is the dissimilatory sulfate reduction pathway in which sulfate (SO(2)) is converted to hydrogen sulfide (HS). Dissimilatory sulfite reductase (dSir), its key enzyme, hosts a unique siroheme-[4Fe-4S] cofactor and catalyzes the six-electron reduction of sulfite (SO(2)) to HS. To explore this reaction, we determined the X-ray structures of dSir from the archaeon Archaeoglobus fulgidus in complex with sulfite, sulfide (S(2)) carbon monoxide (CO), cyanide (CN), nitrite (NO), nitrate (NO), and phosphate (PO(3)). Activity measurements indicated that dSir of A. fulgidus reduces, besides sulfite and nitrite, thiosulfate (SO(2)) and trithionate (SO(2)) and produces the latter two compounds besides sulfide. On this basis, a three-step mechanism was proposed, each step consisting of a two-electron transfer, a two-proton uptake, and a dehydration event. In comparison, the related active site structures of the assimilatory sulfite reductase (aSir)- and dSir-SO(2)complexes reveal different conformations of Argalpha170 and Lysalpha211 both interacting with the sulfite oxygens (its sulfur atom coordinates the siroheme iron), a sulfite rotation of ~60 degrees relative to each other, and different access of solvent molecules to the sulfite oxygens from the active site cleft. Therefore, solely in dSir a further sulfite molecule can be placed in van der Waals contact with the siroheme-ligated sulfite or sulfur-oxygen intermediates necessary for forming thiosulfate and trithionate. Although reported for dSir from several sulfate-reducing bacteria, the in vivo relevance of their formation is questionable. Reaction cycle of the dissimilatory sulfite reductase from Archaeoglobus fulgidus.,Parey K, Warkentin E, Kroneck PM, Ermler U Biochemistry. 2010 Oct 19;49(41):8912-21. PMID:20822098 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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