Angular dependence of electron paramagnetic resonance of an azide-NO complex of cytochrome c oxidase: orientation of the haem-copper axis in cytochrome aa3 from ox heart

William John Ingledew, DJB Hunter, JC Salerno

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3 Citations (Scopus)

Abstract

The orientation dependence of the EPR signals arising from the azide-nitric oxide complex of cytochrome oxidase was investigated using oriented multilayers of mitochondrial membranes from ox heart. Variations in line shape of the Delta M-S = 1 signal of the triplet state were apparent, whilst the Delta M-S = 2 transitions between g = 4.7 and 3.9 varied in intensity as the angle of the applied magnetic field was varied. These half-field signals were maximal with the field parallel to the membrane plane. A model of the bi-liganded azide-nitric oxide complex has been constructed, in which the nitric oxide is bound to the high-spin haem in a bent configuration, with the Fe-N=O plane at 60-90 degrees to the membrane plane and the azide bound to the copper, distal from the haem. In addition, angular variations of the signals at g' = 11 and g' around 3.5, derived from an integer-spin complex, were also observed. (C) 1998 Elsevier Science B.V.

Original languageEnglish
Pages (from-to)55-62
Number of pages8
JournalBiochimica et Biophysica Acta
Volume1364
Publication statusPublished - 14 Apr 1998

Keywords

  • cytochrome oxidase
  • EPR
  • orientation
  • ESCHERICHIA-COLI
  • QUINOL OXIDASE
  • NITRIC-OXIDE
  • BO
  • MEMBRANE
  • BINDING
  • SITE
  • HEME

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