title: Spectroscopic and computational studies of nitrite reductase: proton induced electron transfer and backbonding contributions to reactivity.
abstract: A combination of spectroscopy and DFT calculations has been used to define the geometric and electronic structure of the nitrite bound type 2 (T2) copper site at high and low pH in nitrite reductase from Rhodobacter sphaeroides. At high pH there is no electron transfer from reduced type 1 (T1) to the nitrite bound T2 copper, while protonation triggers T1 --> T2 electron transfer and generation of NO. The DFT calculated reaction coordinate for the N-O bond cleavage in nitrite reduction by the reduced T2 copper suggests that the process is best described as proton transfer triggering electron transfer. Bidentate nitrite binding to copper is calculated to play a major role in activating the reductive cleavage of the nitrite bond through backbonding combined with stabilization of the (-)OH product by coordination to the Cu(2+).
authors.affiliation: Department of Chemistry, Stanford University, Stanford, California 94305, USA.
authors.forename: Somdatta
authors.initials: S
authors.lastname: Ghosh
authors.forename: Abhishek
authors.initials: A
authors.lastname: Dey
authors.forename: Yan
authors.initials: Y
authors.lastname: Sun
authors.forename: Charles P
authors.initials: CP
authors.lastname: Scholes
authors.forename: Edward I
authors.initials: EI
authors.lastname: Solomon
mesh_terms: D020134:Catalytic Domain; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D008958:Models, Molecular; D009572:Nitrite Reductases / Q000737:chemistry* / Q000378:metabolism; D009573:Nitrites / Q000737:chemistry; D011487:Protein Conformation; D012242:Rhodobacter sphaeroides / Q000201:enzymology; D013056:Spectrophotometry, Ultraviolet
chemical_list: D009573:Nitrites; D003300:Copper; D009572:Nitrite Reductases