X-ray structure of the membrane-bound cytochrome c quinol dehydrogenase NrfH reveals novel haem coordination

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Abstract

Oxidation of membrane-bound quinol molecules is a central step in the respiratory electron transport chains used by biological cells to generate ATP by oxidative phosphorylation. A novel family of cytochrome c quinol dehydrogenases that play an important role in bacterial respiratory chains was recognised in recent years. Here, we describe the first structure of a cytochrome from this family, NrfH from Desulfovibrio vulgaris, which forms a stable complex with its electron partner, the cytochrome c nitrite reductase NrfA. One NrfH molecule interacts with one NrfA dimer in an asymmetrical manner, forming a large membrane-bound complex with an overall α 4β2 quaternary arrangement. The menaquinol- interacting NrfH haem is pentacoordinated, bound by a methionine from the CXXCHXM sequence, with an aspartate residue occupying the distal position. The NrfH haem that transfers electrons to NrfA has a lysine residue from the closest NrfA molecule as distal ligand. A likely menaquinol binding site, containing several conserved and essential residues, is identified.

Original languageEnglish
Pages (from-to)5951-5960
Number of pages10
JournalEmbo Journal
Volume25
Issue number24
DOIs
Publication statusPublished - 13 Dec 2006

Keywords

  • Cytochrome c nitrite reductase
  • NapC-NirT family
  • NrfH/NrfA membrane protein complex
  • Quinol dehydrogenase

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