Strange R W, Dodd F E, Abraham Z H, Grossmann J G, Brüser T, Eady R R, Smith B E, Hasnain S S
Molecular Biophysics Group, Daresbury Laboratory, Warrington, Cheshire, UK.
Nat Struct Biol. 1995 Apr;2(4):287-92. doi: 10.1038/nsb0495-287.
Here we investigate the structure of the two types of copper site in nitrite reductase from Alcaligenes xylosoxidans, the molecular organisation of the enzyme when the type-2 copper is absent, and its mode of substrate binding. X-ray absorption studies provide evidence for a fourth ligand at the type-2 Cu, that substrate binds to this site and indicates that this binding does not change the type-1 Cu centre. The substrate replaces a putative water ligand and is accommodated by a lengthening of the Cu-histidine bond by approximately 0.08 A. Modelling suggests a similarity between this unusual type-2 Cu site and the Zn site in carbonic anhydrase and that nitrite is anchored by hydrogen bonds to an unligated histidine present in the type-2 Cu cavity.
