4wjy | pdb_00004wjy

Esherichia coli nitrite reductase NrfA H264N

spinqualitylabelsall models 4wjy, resolution 2.15Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4wjy is a 2 chain structure with sequence from Escherichia coli K-12. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CA, EDO, HEC Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function NRFA_ECOLI Plays a role in nitrite reduction.[HAMAP-Rule:MF_01182] Publication Abstract from PubMed Cytochrome c nitrite reductases perform a key step in the biogeochemical N-cycle by catalyzing the six-electron reduction of nitrite to ammonium. These multiheme cytochromes contain a number of His/His ligated c-hemes for electron transfer and a structurally differentiated heme that provides the catalytic center. The catalytic heme has proximal ligation from lysine, or histidine, and an exchangeable distal ligand bound within a pocket that includes a conserved histidine. Here we describe properties of a penta-heme cytochrome c nitrite reductase in which the distal His has been substituted by Asn. The variant is unable to catalyze nitrite reduction despite retaining the ability to reduce a proposed intermediate in that process, namely, hydroxylamine. A combination of electrochemical, structural and spectroscopic studies reveals that the variant enzyme simultaneously binds nitrite and electrons at the catalytic heme. As a consequence the distal His is proposed to play a key role in orienting the nitrite for N-O bond cleavage. The electrochemical experiments also reveal that the distal His facilitates rapid nitrite binding to the catalytic heme of the native enzyme. Finally it is noted that the thermodynamic descriptions of nitrite- and electron-binding to the active site of the variant enzyme are modulated by the prevailing oxidation states of the His/His ligated hemes. This behavior is likely to be displayed by other multicentered redox enzymes such that there are wide implications for considering the determinants of catalytic activity in this important and varied group of oxidoreductases. Resolution of key roles for the distal pocket histidine in cytochrome C nitrite reductases.,Lockwood CW, Burlat B, Cheesman MR, Kern M, Simon J, Clarke TA, Richardson DJ, Butt JN J Am Chem Soc. 2015 Mar 4;137(8):3059-68. doi: 10.1021/ja512941j. Epub 2015 Feb, 18. PMID:25658043 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Cytochrome c nitrite reductase

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