2yax | pdb_00002yax

IODOACETAMIDE INHIBITED SULFUR OXYGENASE REDUCTASE

spinqualitylabelsall models 2yax, resolution 1.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2yax is a 6 chain structure with sequence from Acidianus ambivalens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: FE NonStd Res: CSS, YCM Related: 2cb2, 2yav, 2yaw Activity: Sulfur oxygenase/reductase, with EC number 1.13.11.55 Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed Background: The sulfur oxygenase reductase (SOR) is the initial enzyme of the sulfur oxidation pathway in the thermoacidophilic Archaeon Acidianus ambivalens. The SOR catalyzes an oxygen-dependent sulfur disproportionation to H(2)S, sulfite and thiosulfate. The spherical, hollow, cytoplasmic enzyme is composed of 24 identical subunits with an active site pocket each comprising a mononuclear non-heme iron site and a cysteine persulfide. Substrate access and product exit occur via apolar chimney-like protrusions at the fourfold symmetry axes, via narrow polar pores at the threefold symmetry axes and via narrow apolar pores within in each subunit. In order to investigate the function of the pores we performed site-directed mutagenesis and inhibitor studies. Results: Truncation of the chimney-like protrusions resulted in an up to sevenfold increase in specific enzyme activity compared to the wild type. Replacement of the salt bridge-forming Arg(99) residue by Ala at the threefold symmetry axes doubled the activity and introduced a bias toward reduced reaction products. Replacement of Met(296) and Met(297), which form the active site pore, lowered the specific activities by 25-55% with the exception of an M(296)V mutant. X-ray crystallography of SOR wild type crystals soaked with inhibitors showed that Hg(2+) and iodoacetamide (IAA) bind to cysteines within the active site, whereas Zn(2+) binds to a histidine in a side channel of the enzyme. The Zn(2+) inhibition was partially alleviated by mutation of the His residue. Conclusions: The expansion of the pores in the outer shell led to an increased enzyme activity while the integrity of the active site pore seems to be important. Hg(2+) and IAA block cysteines in the active site pocket, while Zn(2+) interferes over a distance, possibly by restriction of protein flexibility or substrate access or product exit. Substrate pathways and mechanisms of inhibition in the sulfur oxygenase reductase of acidianus ambivalens.,Veith A, Urich T, Seyfarth K, Protze J, Frazao C, Kletzin A Front Microbiol. 2011;2:37. Epub 2011 Mar 7. PMID:21747782 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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