The 2.3 angstrom X-ray structure of nitrite reductase from Achromobacter cycloclastes.
The three-dimensional crystal structure of the copper-containing nitrite reductase (NIR) from Achromobacter cycloclastes has been determined to 2.3 angstrom (A) resolution by isomorphous replacement. The monomer has two Greek key beta-barrel domains similar to that of plastocyanin and contains two copper sites. The enzyme is a trimer both in the crystal and in solution. The two copper atoms in the monomer comprise one type I copper site (Cu-I; two His, one Cys, and one Met ligands) and one putative type II copper site (Cu-II; three His and one solvent ligands). Although ligated by adjacent amino acids Cu-I and Cu-II are approximately 12.5 A apart. Cu-II is bound with nearly perfect tetrahedral geometry by residues not within a single monomer, but from each of two monomers of the trimer. The Cu-II site is at the bottom of a 12 A deep solvent channel and is the site to which the substrate (NO2-) binds, as evidenced by difference density maps of substrate-soaked and native crystals.
Godden
J W
JW
Department of Biochemistry, University of Washington, Seattle 98195.
Turley
S
S
Teller
D C
DC
Adman
E T
ET
Liu
M Y
MY
Payne
W J
WJ
LeGall
J
J
D000421:Alcaligenes / Q000201:enzymology*; D000595:Amino Acid Sequence; D003300:Copper / Q000032:analysis; D008958:Models, Molecular; D008970:Molecular Weight; D009572:Nitrite Reductases / Q000737:chemistry*; D011487:Protein Conformation; D014961:X-Ray Diffraction
D003300:Copper; D009572:Nitrite Reductases