3 research outputs found

    Structure of the Membrane-intrinsic Nitric Oxide Reductase from <i>Roseobacter denitrificans</i>

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    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 <i>b</i><sub>3</sub> within the active site. In NOR, this metal is iron (Fe<sub>B</sub>), whereas in COX, it is copper (Cu<sub>B</sub>). The purified NOR of <i>Roseobacter denitrificans</i> 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 <i>Roseobacter denitrificans</i> 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
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