3mmc | pdb_00003mmc

Structure of the dissimilatory sulfite reductase from Archaeoglobus fulgidus

spinqualitylabelsall models 3mmc, resolution 2.04Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3mmc is a 4 chain structure with sequence from Archaeoglobus fulgidus. This structure supersedes the now removed PDB entry 3c7b. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: GOL, SF4, SRM Related: 3c7b Activity: Hydrogensulfite reductase, with EC number 1.8.99.3 Resources: FirstGlance, OCA, RCSB, PDBsum 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 Conservation of energy based on the reduction of sulfate is of fundamental importance for the biogeochemical sulfur cycle. A key enzyme of this ancient anaerobic process is the dissimilatory sulfite reductase (dSir), which catalyzes the six-electron reduction of sulfite to hydrogen sulfide under participation of a unique magnetically coupled siroheme-[4Fe-4S] center. We determined the crystal structure of the enzyme from the sulfate-reducing archaeon Archaeoglobus fulgidus at 2-A resolution and compared it with that of the phylogenetically related assimilatory Sir (aSir). dSir is organized as a heterotetrameric (alphabeta)(2) complex composed of two catalytically independent alphabeta heterodimers. In contrast, aSir is a monomeric protein built of two fused modules that are structurally related to subunits alpha and beta except for a ferredoxin domain inserted only into the subunits of dSir. The [4Fe-4S] cluster of this ferredoxin domain is considered as the terminal redox site of the electron transfer pathway to the siroheme-[4Fe-4S] center in dSir. While aSir binds one siroheme-[4Fe-4S] center, dSir harbors two of them within each alphabeta heterodimer. Surprisingly, only one siroheme-[4Fe-4S] center in each alphabeta heterodimer is catalytically active, whereas access to the second one is blocked by a tryptophan residue. The spatial proximity of the functional and structural siroheme-[4Fe-4S] centers suggests that the catalytic activity at one active site was optimized during evolution at the expense of the enzymatic competence of the other. The sulfite binding mode and presumably the mechanism of sulfite reduction appear to be largely conserved between dSir and aSir. In addition, a scenario for the evolution of Sirs is proposed. Structure of the dissimilatory sulfite reductase from the hyperthermophilic archaeon Archaeoglobus fulgidus.,Schiffer A, Parey K, Warkentin E, Diederichs K, Huber H, Stetter KO, Kroneck PM, Ermler U J Mol Biol. 2008 Jun 20;379(5):1063-74. Epub 2008 May 20. PMID:18495156 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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