Reductive nitrosylation of the cardiolipin-ferric cytochrome c complex

Paolo Ascenzi, Maria Marino, Chiara Ciaccio, Roberto Santucci, Massimo Coletta

Research output: Contribution to journalArticlepeer-review


Native horse heart cytochrome c (cytc) displays a very low reactivity toward ligands and does not exhibit catalytic properties. However, upon bovine cardiolipin (CL) binding, cytc achieves myoglobin-like properties. Here, NO binding to CL-cytc(III) between pH 7.2 and 9.5, at 20°C, is reported. At pH 7.2, CL-cytc(III) undergoes reversible nitrosylation, whereas between pH 7.9 and 9.5 CL-cytc(III) undergoes irreversible reductive nitrosylation leading to the formation of CL-cytc(II)-NO. Over the whole pH range explored, first-order kinetics of NO binding to CL-cytc(III) (k=9.3 s-1) indicates that ligand binding is limited by the cleavage of the weak heme-Fe distal bond. Between pH 7.9 and 9.5, nitrosylated CL-cytc(III) converts to the ligand-free ferrous derivative (CL-cytc(II)), this process being pH-dependent (h OH-=3.0 × 103 M-1 s-1). Then, CL-cytc(II) converts to nitrosylated CL-cytc(II), in the presence of NO excess. The value of the second-order rate constant for CL-cytc(II) nitrosylation is essentially pH-independent, the average value of lon being 1.4 × 107 M-1 s-1. These results agree with the view that CL-cytc nitrosylation may play a role in apoptosis regulation.

Original languageEnglish
Pages (from-to)438-447
Number of pages10
JournalIUBMB Life
Issue number6
Publication statusPublished - 2014


  • cardiolipin-ferric cytochrome c complex
  • kinetics.
  • NO binding to the cardiolipin-ferric cytochrome c complex
  • NO binding to the cardiolipin-ferrous cytochrome c complex
  • reductive nitrosylation

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Clinical Biochemistry
  • Molecular Biology
  • Genetics
  • Medicine(all)


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