title: A needle in a haystack: the active site of the membrane-bound complex cytochrome c nitrite reductase.
abstract: Cytochrome c nitrite reductase is a multicenter enzyme that uses a five-coordinated heme to perform the six-electron reduction of nitrite to ammonium. In the sulfate reducing bacterium Desulfovibrio desulfuricans ATCC 27774, the enzyme is purified as a NrfA2NrfH complex that houses 14 hemes. The number of closely-spaced hemes in this enzyme and the magnetic interactions between them make it very difficult to study the active site by using traditional spectroscopic approaches such as EPR or UV-Vis. Here, we use both catalytic and non-catalytic protein film voltammetry to simply and unambiguously determine the reduction potential of the catalytic heme over a wide range of pH and we demonstrate that proton transfer is coupled to electron transfer at the active site.
authors.affiliation: REQUIMTE, CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516, Monte de Caparica, Portugal.
authors.forename: M Gabriela
authors.initials: MG
authors.lastname: Almeida
authors.forename: Célia M
authors.initials: CM
authors.lastname: Silveira
authors.forename: Bruno
authors.initials: B
authors.lastname: Guigliarelli
authors.forename: Patrick
authors.initials: P
authors.lastname: Bertrand
authors.forename: José J G
authors.initials: JJ
authors.lastname: Moura
authors.forename: Isabel
authors.initials: I
authors.lastname: Moura
authors.forename: Christophe
authors.initials: C
authors.lastname: Léger
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification; D001665:Binding Sites; D002384:Catalysis; D045263:Cytochromes a1 / Q000737:chemistry* / Q000302:isolation & purification; D003575:Cytochromes c1 / Q000737:chemistry* / Q000302:isolation & purification; D045285:Desulfovibrio desulfuricans / Q000201:enzymology*; D006418:Heme / Q000737:chemistry*; D009565:Nitrate Reductases / Q000737:chemistry* / Q000302:isolation & purification; D011199:Potentiometry; D011522:Protons
chemical_list: D001426:Bacterial Proteins; D011522:Protons; D006418:Heme; D045263:Cytochromes a1; D003575:Cytochromes c1; D009565:Nitrate Reductases; C054690:nitrate reductase (cytochrome)