Structure of the binuclear heme iron-copper site in the quinol-oxidizing cytochrome aa3 from Bacillus subtilis

Linda Powers, Marko Lauraeus, Konda S. Reddy, Britton Chance, Mårten Wikström

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

Cytochrome aa3-600 is a terminal quinol oxidase of Bacillus subtilis, belonging to the large family of structurally and functionally related respiratory enzymes to which the mitochondrial cytochrome c oxidase also belongs. However, the CuA center typical of the cytochrome c oxidases is lacking from cytochrome aa3-600. The presence of only one copper, viz. CuB of the binuclear heme iron-copper site, makes cytochrome aa3-600 especially suitable for XAS analysis of this structure. Cu and Fe XAS data for fully oxidized cytochrome aa3-600 indicate a structure for the binuclear site similar to that previously reported for mitochondrial cytochrome c oxidase (see Powers et al. (1981) Biophys. J. 34, 465-468). Heme Fea3 has a proximal histidine nitrogen ligand 2.10 ± 0.02 A ̊ from the iron, and a distal S or Cl ligand at 2.36 ± 0.03 A ̊. The latter is also a ligand of CuB (2.21 ± 0.02 A ̊), and apparently forms a bridge between the two metals which are 3.70 ± 0.06 A ̊ apart. CuB has two more close-lying ligands at 1.95 ± 0.02 A ̊, which are likely histidine nitrogens. The similarity between EXAFS of CuB and type 1 'blue' copper is contrasted to EPR and optical spectroscopic properties of CuB, and the nature of the bridging ligand is discussed.

Original languageEnglish (US)
Pages (from-to)504-512
Number of pages9
JournalBBA - Bioenergetics
Volume1183
Issue number3
DOIs
StatePublished - Jan 4 1994
Externally publishedYes

Keywords

  • Cytochrome oxidase
  • EXAFS
  • Heme
  • Quinol oxidase

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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