A needle in a haystack: the active site of the membrane-bound complex cytochrome c nitrite reductase |
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Authors: | Almeida M Gabriela Silveira Célia M Guigliarelli Bruno Bertrand Patrick Moura José J G Moura Isabel Léger Christophe |
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Institution: | REQUIMTE, CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516, Monte de Caparica, Portugal. |
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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. |
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Keywords: | Cytochromes Protein film voltammetry Penta-heme nitrite reductase Electron transfer |
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