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A needle in a haystack: The active site of the membrane‐bound complex cytochrome c nitrite reductase
Author(s) -
Almeida M. Gabriela,
Silveira Célia M.,
Guigliarelli Bruno,
Bertrand Patrick,
Moura José J.G.,
Moura Isabel,
Léger Christophe
Publication year - 2007
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2006.12.023
Subject(s) - chemistry , nitrite reductase , electron transfer , nitrite , heme , desulfovibrio , active site , catalysis , electron transport chain , enzyme , haystack , reductase , stereochemistry , biochemistry , photochemistry , nitrate reductase , organic chemistry , sulfate , nitrate , world wide web , computer science
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 NrfA 2 NrfH 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.