1aop
From Proteopedia
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SULFITE REDUCTASE STRUCTURE AT 1.6 ANGSTROM RESOLUTION
Overview
Fundamental chemical transformations for biogeochemical cycling of sulfur, and nitrogen are catalyzed by sulfite and nitrite reductases. The, crystallographic structure of Escherichia coli sulfite reductase, hemoprotein (SiRHP), which catalyzes the concerted six-electron reductions, of sulfite to sulfide and nitrite to ammonia, was solved with, multiwavelength anomalous diffraction (MAD) of the native siroheme and, Fe4S4 cluster cofactors, multiple isomorphous replacement, and, selenomethionine sequence markers. Twofold symmetry within the, 64-kilodalton polypeptide generates a distinctive three-domain alpha/beta, fold that controls cofactor assembly and reactivity. Homology regions, conserved between the symmetry-related halves of SiRHP and among other, sulfite and nitrite reductases revealed key residues for stability and, function, and identified a sulfite or nitrite reductase repeat (SNiRR), common to a redox-enzyme superfamily. The saddle-shaped siroheme shares a, cysteine thiolate ligand with the Fe4S4 cluster and ligates an unexpected, phosphate anion. In the substrate complex, sulfite displaces phosphate and, binds to siroheme iron through sulfur. An extensive hydrogen-bonding, network of positive side chains, water molecules, and siroheme, carboxylates activates S-O bonds for reductive cleavage.
About this Structure
1AOP is a Single protein structure of sequence from Escherichia coli with PO4, K, SF4 and SRM as ligands. This structure superseeds the now removed PDB entry 1GEO. Active as Sulfite reductase (NADPH), with EC number 1.8.1.2 Known structural/functional Sites: and . Full crystallographic information is available from OCA.
Reference
Sulfite reductase structure at 1.6 A: evolution and catalysis for reduction of inorganic anions., Crane BR, Siegel LM, Getzoff ED, Science. 1995 Oct 6;270(5233):59-67. PMID:7569952[[Category: [4fe-4s]]]
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