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Cardiolipin modulates allosterically peroxynitrite detoxification by horse heart cytochrome c

Paolo Ascenzi1, Chiara Ciaccio, Federica Sinibaldi

  • 1Department of Biology and Interdepartmental Laboratory for Electron Microscopy, University Roma Tre, I-00146 Roma, Italy. ascenzi@uniroma3.it

Biochemical and Biophysical Research Communications
|November 30, 2010
PubMed

Insights

Cardiolipin (CL) binding to cytochrome c (cytc) enables ferric cytc to catalyze peroxynitrite isomerization. This interaction suggests CL-cytc may influence apoptosis by modulating lipid peroxidation and reactive nitrogen species.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cellular Signaling

Background:

  • Cytochrome c (cytc) undergoes significant structural and functional changes upon binding cardiolipin (CL).
  • These changes include altered redox potential, modified heme coordination, and acquisition of peroxidase activity.
  • The role of CL in mediating cytc's interaction with reactive nitrogen species is not fully understood.

Purpose of the Study:

  • To investigate the effect of cardiolipin (CL) on the isomerization of peroxynitrite by ferric cytochrome c (cytc-Fe(III)).
  • To characterize the kinetics and binding parameters of the CL-cytc-Fe(III)-peroxynitrite interaction.

Main Methods:

  • Spectroscopic analysis of ferric cytochrome c (cytc-Fe(III)) in the presence and absence of cardiolipin (CL).
  • Kinetic assays to measure the rate of peroxynitrite isomerization.
  • Determination of binding constants for cardiolipin (CL) to ferric cytc (cytc-Fe(III)).

Main Results:

  • Hexa-coordinated cytc-Fe(III) does not catalyze peroxynitrite isomerization without CL.
  • CL facilitates cytc-Fe(III)-mediated peroxynitrite isomerization in a dose-dependent manner, inducing penta-coordination of the heme-Fe(III).
  • The second-order rate constant (k(on)) for CL-cytc-Fe(III)-mediated isomerization is (3.2±0.4)×10^5 M^-1 s^-1, with an apparent dissociation constant (Kd) of (5.1±0.8)×10^-5 M for CL binding.

Conclusions:

  • Cardiolipin (CL) binding is essential for ferric cytochrome c (cytc-Fe(III)) to catalyze peroxynitrite isomerization.
  • The CL-cytc complex may play a dual role in apoptosis, potentially promoting lipid peroxidation or scavenging reactive nitrogen species like peroxynitrite.

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