Nitric oxide binding to ferrous native horse heart cytochrome c and to its carboxymethylated derivative: A spectroscopic and thermodynamic Study

Paolo Ascenzi, Massimo Coletta, Roberto Santucci, Francesca Polizio, Alessandro Desideri

Research output: Contribution to journalArticlepeer-review

Abstract

Nitric oxide binding to ferrous native horse heart cytochrome c and to its carboxymethylated derivative has been investigated quantitatively by EPR and absorbance spectroscopy. The X-band EPR spectra and the absorption spectra in the Soret region of the nitrosylated derivative of ferrous native and carboxymethylated cytochrome c display the same basic characteristics reported for the beef heart cytochrome a3 in cytochrome c oxidase, and horseradish and baker's yeast cytochrome c peroxidase, as well as the high affinity form of oxygen carrying proteins. Values of the dissociation equilibrium constant for nitrosylation of ferrous native and carboxymethylated cytochrome c are 8.2 × 10-6 M and ≤ 5 × 10-8 M, respectively, at pH 7.0 and 10°C. The results here reported represent clearcut evidence for the nitric oxide-induced cleavage of the FeMet80 bond in ferrous native cytochrome c, and allow estimation of the free energy associated to the heme-iron sixth coordination bond ( > 10 kJ mol-1, at 10°C).

Original languageEnglish
Pages (from-to)273-280
Number of pages8
JournalJournal of Inorganic Biochemistry
Volume53
Issue number4
DOIs
Publication statusPublished - 1994

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

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