2pp7
| |||||||
| , resolution 1.65Å | |||||||
|---|---|---|---|---|---|---|---|
| Sites: | , , , , , , , , , , , , , , , , , , and | ||||||
| Ligands: | , , , | ||||||
| Gene: | nirK, nir (Alcaligenes faecalis) | ||||||
| Activity: | Nitrite reductase (NO-forming), with EC number 1.7.2.1 | ||||||
| Domains: | Cu-oxidase_3, Cu-oxidase | ||||||
| Related: | 1SNR, 1SJM, 2FJS
| ||||||
| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Crystal structure of anaerobically manipulated wild type oxidized AfNiR (acetate bound)
OverviewOverview
The interaction of copper-containing dissimilatory nitrite reductase from Alcaligenes faecalis S-6 ( AfNiR) with each of five small molecules was studied using crystallography and steady-state kinetics. Structural studies revealed that each small molecule interacted with the oxidized catalytic type 2 copper of AfNiR. Three small molecules (formate, acetate and nitrate) mimic the substrate by having at least two oxygen atoms for bidentate coordination to the type 2 copper atom. These three anions bound to the copper ion in the same asymmetric, bidentate manner as nitrite. Consistent with their weak inhibition of the enzyme ( K i >50 mM), the Cu-O distances in these AfNiR-inhibitor complexes were approximately 0.15 A longer than that observed in the AfNiR-nitrite complex. The binding mode of each inhibitor is determined in part by steric interactions with the side chain of active site residue Ile257. Moreover, the side chain of Asp98, a conserved residue that hydrogen bonds to type 2 copper-bound nitrite and nitric oxide, was either disordered or pointed away from the inhibitors. Acetate and formate inhibited AfNiR in a mixed fashion, consistent with the occurrence of second acetate binding site in the AfNiR-acetate complex that occludes access to the type 2 copper. A fourth small molecule, nitrous oxide, bound to the oxidized metal in a side-on fashion reminiscent of nitric oxide to the reduced copper. Nevertheless, nitrous oxide bound at a farther distance from the metal. The fifth small molecule, azide, inhibited the reduction of nitrite by AfNiR most strongly ( K ic = 2.0 +/- 0.1 mM). This ligand bound to the type 2 copper center end-on with a Cu-N c distance of approximately 2 A, and was the only inhibitor to form a hydrogen bond with Asp98. Overall, the data substantiate the roles of Asp98 and Ile257 in discriminating substrate from other small anions.
About this StructureAbout this Structure
2PP7 is a Single protein structure of sequence from Alcaligenes faecalis. Full crystallographic information is available from OCA.
ReferenceReference
Conserved Active Site Residues Limit Inhibition of a Copper-Containing Nitrite Reductase by Small Molecules., Tocheva EI, Eltis LD, Murphy ME, Biochemistry. 2008 Mar 22;. PMID:18358002
Page seeded by OCA on Wed Apr 2 11:57:50 2008