title: Paracoccus pantotrophus NapC can reductively activate cytochrome cd1 nitrite reductase.
abstract: The oxidized "as isolated" form of Paracoccus pantotrophus cytochrome cd1 nitrite reductase has a bis-histidinyl coordinated c heme and a histidine/tyrosine coordinated d1 heme. This form of the enzyme has previously been shown to be kinetically incompetent. Upon reduction, the coordination of both hemes changes and the enzyme is kinetically activated. Here, we show that P. pantotrophus NapC, a tetraheme c-type cytochrome belonging to a large family of such proteins, is capable of reducing, and hence activating, "as isolated" cytochrome cd1. NapC is the first protein from P. pantotrophus identified as being capable of this activation step and, given the periplasmic co-location and co-expression of the two proteins, is a strong candidate to be a physiological activation partner.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Zajicek
authors.forename: James W A
authors.initials: JW
authors.lastname: Allen
authors.forename: Michaël L
authors.initials: ML
authors.lastname: Cartron
authors.forename: David J
authors.initials: DJ
authors.lastname: Richardson
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Ferguson
mesh_terms: D002384:Catalysis; D003580:Cytochromes; D045304:Cytochromes c / Q000737:chemistry* / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D004789:Enzyme Activation; D006418:Heme / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D009572:Nitrite Reductases / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D042084:Paracoccus pantotrophus / Q000378:metabolism*; D013053:Spectrophotometry; D013997:Time Factors; D014443:Tyrosine / Q000737:chemistry
chemical_list: D003580:Cytochromes; D008024:Ligands; D014443:Tyrosine; D006418:Heme; D006639:Histidine; D045304:Cytochromes c; D009572:Nitrite Reductases; C028123:nitrite reductase (NO-forming); D003576:Electron Transport Complex IV; D010100:Oxygen