1wa2

File:1wa2.gif

spinqualitylabelsall models 1wa2, resolution 1.72Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CRYSTAL STRUCTURE OF H313Q MUTANT OF ALCALIGENES XYLOSOXIDANS NITRITE REDUCTASE WITH NITRITE BOUND

OverviewOverview

Dissimilatory nitrite reductase catalyses the reduction of nitrite to, nitric oxide within the key biological process of denitrification. We, present biochemical and structural results on two key mutants, one, postulated to be important for the interaction with the partner protein, and the other for substrate entry. Trp138, adjacent to one of the type-1, Cu ligands, is one of the residues surrounding a small depression, speculated to be important in complex formation with the physiological, redox partners, azurin I and II. Our data reveal that the Trp138His mutant, is fully active using methyl viologen as an artificial electron donor, but, there is a large decrease in activity using azurin I. These observations, together with its crystal structure at a high resolution of 1.6 A confirm, the importance of Trp138 in electron transfer and thus in productive, interaction with azurin. A "hydrophobic pocket" on the protein surface has, been identified as the channel through which nitrite may be guided to the, catalytic type-2 Cu site. Glu133 and His313 at the opening of the pocket, are conserved among most blue and green copper nitrite reductases, (CuNiRs). The failure to soak the substrate into our high-resolution, crystal form of native and mutant CuNiRs has been linked to the, observation of an extraneous poly(ethylene glycol) (PEG) molecule, interacting with His313. We present the crystal structure of His313Gln and, the substrate-bound mutant at high resolutions of 1.65 and 1.72 A, respectively. The observation of the substrate-bound structure for the, His313Gln mutant and inhibitory studies with PEG establishes the role of, the hydrophobic pocket as the port of substrate entry.

About this StructureAbout this Structure

1WA2 is a Single protein structure of sequence from Achromobacter xylosoxidans with CU, ZN, NO2, SO4 and MES as ligands. Structure known Active Site: AC1. Full crystallographic information is available from OCA.

ReferenceReference

Insights into redox partner interactions and substrate binding in nitrite reductase from Alcaligenes xylosoxidans: crystal structures of the Trp138His and His313Gln mutants., Barrett ML, Harris RL, Antonyuk S, Hough MA, Ellis MJ, Sawers G, Eady RR, Hasnain SS, Biochemistry. 2004 Dec 28;43(51):16311-9. PMID:15610025

Page seeded by OCA on Mon Nov 5 17:30:20 2007