X-ray structure of azide-bound fully oxidized cytochrome c oxidase from bovine heart at 2.9 A resolution

Acta Crystallogr D Biol Crystallogr. 2000 May;56(Pt 5):529-35. doi: 10.1107/s0907444900002213.

Abstract

Two azide ions were identified, one between the Fe and Cu atoms in the O(2)-reduction site and the other at the transmembrane surface of the enzyme, in the crystal structure of the azide-bound form of bovine heart cytochrome c oxidase at 2.9 A resolution. Two geometries, a mu-1,3 type geometry between the Fe and Cu atoms and a terminal geometry on the Fe atom, are equally possible for an azide ion in the O(2)--reduction site. The other azide molecule was hydrogen bonded to an amide group of an asparagine and a hydroxyl group of tyrosine in a mu-1,1 type geometry. The antisymmetric infrared bands arising from these azide ions, which show essentially identical intensity [Yoshikawa & Caughey (1992), J. Biol. Chem. 267, 9757-9766], strongly suggest terminal binding of the azide to Fe. The electron density of all three imidazole ligands to Cu(B) was clearly seen in the electron-density map of the azide-bound form of bovine heart enzyme, in contrast to the crystal structure of the azide-bound form of the bacterial enzyme [Iwata et al. (1995), Nature (London), 376, 660-669], which lacks one of the three imidazole ligands to Cu(B).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Azides
  • Binding Sites
  • Cattle
  • Computer Graphics
  • Copper
  • Crystallography, X-Ray
  • Electron Transport Complex IV / chemistry*
  • Electron Transport Complex IV / metabolism
  • Iron
  • Mitochondria, Heart / enzymology*
  • Models, Molecular
  • Oxidation-Reduction
  • Protein Conformation

Substances

  • Azides
  • Copper
  • Iron
  • Electron Transport Complex IV