title: Structure of the Membrane-intrinsic Nitric Oxide Reductase from Roseobacter denitrificans.
abstract: Membrane-intrinsic nitric oxide reductases (NORs) are key components of bacterial denitrification pathways with a close evolutionary relationship to the cytochrome oxidase (COX) complex found in aerobic respiratory chains. A key distinction between COX and NOR is the identity of the metal directly opposite heme b3 within the active site. In NOR, this metal is iron (FeB), whereas in COX, it is copper (CuB). The purified NOR of Roseobacter denitrificans contains copper and has modest oxidase activity, raising the possibility that a COX-like active site might have independently arisen within the context of a NOR-like protein scaffold. Here we present the crystal structure of the Roseobacter denitrificans NorBC complex and anomalous scattering experiments probing the identity of each metal center. Our results refute the hypothesis that copper occupies the active site and instead reveal a new metal center in the small subunit not seen in any other NOR or COX.
authors.affiliation: Department of Pathology, University of Cambridge , Cambridge, U.K.
authors.forename: Allister
authors.initials: A
authors.lastname: Crow
authors.affiliation: Department of Biology, Kyushu University , Fukuoka, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: Department of Biology, Kyushu University , Fukuoka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Arata
authors.affiliation: Lead Pharma , Pivot Park, 5349AC Oss, The Netherlands.
authors.forename: Arthur
authors.initials: A
authors.lastname: Oubrie
mesh_terms: D020134:Catalytic Domain; D002462:Cell Membrane / Q000378:metabolism*; D003300:Copper / Q000378:metabolism*; D003460:Crystallization; D018360:Crystallography, X-Ray; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism; D006418:Heme / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D041904:Roseobacter / Q000201:enzymology*
chemical_list: D006418:Heme; D003300:Copper; D007501:Iron; D010088:Oxidoreductases; C034747:nitric-oxide reductase; D003576:Electron Transport Complex IV