title: Atomic resolution structures of resting-state, substrate- and product-complexed Cu-nitrite reductase provide insight into catalytic mechanism.
abstract: Copper-containing nitrite reductases catalyze the reduction of nitrite to nitric oxide (NO), a key step in denitrification that results in the loss of terrestrial nitrogen to the atmosphere. They are found in a wide variety of denitrifying bacteria and fungi of different physiology from a range of soil and aquatic ecosystems. Structural analysis of potential intermediates in the catalytic cycle is an important goal in understanding enzyme mechanism. Using "crystal harvesting" and substrate-soaking techniques, we have determined atomic resolution structures of four forms of the green Cu-nitrite reductase, from the soil bacterium Achromobacter cycloclastes. These structures are the resting state of the enzyme at 0.9 A, two species exhibiting different conformations of nitrite bound at the catalytic type 2 Cu, one of which is stable and also has NO present, at 1.10 A and 1.15 A, and a stable form with the product NO bound side-on to the catalytic type 2 Cu, at 1.12 A resolution. These structures provide incisive insights into the initial binding of substrate, its repositioning before catalysis, bond breakage (O-NO), and the formation of a stable NO adduct.
authors.affiliation: Molecular Biophysics Group, Council for the Central Laboratory of the Research Councils Daresbury Laboratory, Warrington WA4 4AD, United Kingdom.
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Antonyuk
authors.forename: Richard W
authors.initials: RW
authors.lastname: Strange
authors.forename: Gary
authors.initials: G
authors.lastname: Sawers
authors.forename: Robert R
authors.initials: RR
authors.lastname: Eady
authors.forename: S Samar
authors.initials: SS
authors.lastname: Hasnain
mesh_terms: D042422:Achromobacter cycloclastes / Q000201:enzymology*; D002384:Catalysis; D003460:Crystallization; D008958:Models, Molecular; D009569:Nitric Oxide / Q000378:metabolism; D009572:Nitrite Reductases / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D013379:Substrate Specificity
chemical_list: D009569:Nitric Oxide; D009572:Nitrite Reductases; C052695:nitrite reductase, copper-containing