2xxg

STRUCTURE OF THE N90S MUTANT OF NITRITE REDUCTASE FROM ALCALIGENES XYLOSOXIDANS

spinqualitylabelsall models 2xxg, resolution 1.60Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2xxg is a 2 chain structure with sequence from Achromobacter xylosoxidans. This structure supersedes the now removed PDB entry 2jl0. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CU, MES, PEG, PG4, ZN NonStd Res: PCA Related: 2xx1, 1gs8, 2vm3, 1oe2, 1gs7, 1wa1, 2bp8, 1wa2, 1oe1, 2bp0, 2jl3, 1ndt, 1haw, 1wae, 1oe3, 2xx0, 2xwz, 1hau, 2jfc, 1gs6, 2bo0, 1bq5, 2xxf, 2vw6, 2vn3, 2vw7, 2vmj, 2vw4, 2vm4, 1wa0 Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed Proton and electron delivery to the catalytic site and their associated pathways are crucial elements in understanding the mechanisms of redox enzymes. Two distinct proton channels have previously been identified in copper nitrite reductases based on high- to atomic-resolution crystal structures. These were assigned as the "primary" and "high-pH" proton channels and link the catalytic type 2 Cu center to the enzyme surface. Residue His254 has been identified as a key residue in the primary proton channel from the catalytic T2Cu site to the surface, while Asn90 is thought to be a key residue in the high-pH channel. The structure of the His254Phe mutant was previously determined to 1.85 A resolution, revealing disruption in the H-bonding network of the primary proton channel. The effect of the mutation on proton transfer was not established as the T2Cu center was unusually occupied by Zn. New growth protocols have now led to the incorporation of copper at this site, and here we present spectroscopic, catalytic activity, and structural data for the Cu-loaded H254F mutant of AxNiR. Surprisingly, this species exhibits essentially full catalytic activity, despite the clear disruption of the primary proton channel. In contrast, the Asn90Ser mutation disrupts H-bonding in the high-pH proton channel and results in an approximately 70% decrease in specific activity. These mutations do not change the apparent K(m) for nitrite, and thus, these data clearly demonstrate a role for the high-pH proton channel in the delivery of protons to the catalytic T2Cu center at physiological pH values; it may in fact be the main source of protons to the T2Cu center. Identification of the proton channel to the active site type 2 Cu center of nitrite reductase: structural and enzymatic properties of the His254Phe and Asn90Ser mutants.,Hough MA, Eady RR, Hasnain SS Biochemistry. 2008 Dec 23;47(51):13547-53. PMID:19053252 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Nitric reductase

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