title: Insights into unknown foreign ligand in copper nitrite reductase.
abstract: Bifunctional copper nitrite reductase (CuNIR) catalyzes nitrite reduction to nitric oxide and dioxygen reduction to hydrogen peroxide. In contrast to the well-researched nitrite reduction mechanism, the oxygen reduction mechanism in CuNIR has been totally unknown, because mononuclear copper-oxygen complexes decompose so readily that their visualization has been challenging. Here, we provide spectroscopic evidence that a foreign ligand binds to the catalytic copper (T2Cu) site of CuNIR, and determine CuNIR structures displaying a diatomic molecule on T2Cu. This unknown ligand can be interpreted as dioxygen and may provide insights into the oxygen reduction mechanism of CuNIR.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Yohta
authors.initials: Y
authors.lastname: Fukuda
authors.affiliation: Interdisciplinary Program for Biomedical Sciences, Institute for Academic Initiatives, Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Ka Man
authors.initials: KM
authors.lastname: Tse
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan; Interdisciplinary Program for Biomedical Sciences, Institute for Academic Initiatives, Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kado
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Mizohata
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Matsumura
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. Electronic address: inouet@chem.eng.osaka-u.ac.jp.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Inoue
mesh_terms: D018360:Crystallography, X-Ray; D008024:Ligands; D009572:Nitrite Reductases / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet
chemical_list: D008024:Ligands; D009572:Nitrite Reductases; C052695:nitrite reductase, copper-containing
keywords: Copper; Enzyme; Structural biology; X-ray crystallography