Probing axial ligands in ferric haemoproteins: An ESR study of myoglobin and horseradish peroxidase in H2 17O

S. Vuk-Pavlović, Y. Siderer

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Abstract

Substitution of H2 16O by H2 17O induces a substantial broadening of the high-field line in the electron-spin resonance spectrum of ferric myoglobin due to the presence of H2 17O at the axial ligand-site. Computer simulations of the experimental spectra yielded the values of the reciprocal relaxation time T2 -1 = 7.8 G and the 17O-hyperfine coupling constant A = 18 ± 1 G. Under identical experimental conditions no effect of H2 17O was observed in horseradish peroxidase. The latter finding excludes the possibility that a water molecule is liganded to the peroxidase haem-iron and supports either the idea that both axial ligands are amino acid residues or that the haem in ferric horseradish peroxidase is pentacoordinate.

Original languageEnglish (US)
Pages (from-to)885-889
Number of pages5
JournalBiochemical and Biophysical Research Communications
Volume79
Issue number3
DOIs
StatePublished - Dec 7 1977

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ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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