Hydrogen peroxide-Induced Gain of Peroxidase Activity of Cytochrome c upon Phosphate-Mediated Binding to Zwitterionic Lipids: Implications for Apoptosis

DAIANA A. CAPDEVILA; WALDEMAR A. MARMISOLLÉ; FLORENCIA TOMASINA; VERÓNICA DEMICHELI; RAFAEL RADI; DANIEL H. MURGIDA

Paris

Conferencia; The Federation of European Biochemical Societies (FEBS), EMBO 2014 Conference; 2014

The Federation of European Biochemical Societies

Cytochrome c (Cyt-c) has been shown to participate in cardiolipin (CL) oxidation and, therefore, in mitochondrial membrane permeabilization during the early events of apoptosis. The gain of peroxidatic activity has been ascribed to CL/Cyt-c interactions which, nevertheless, are also ubiquitous in healthy cells, thereby posing the question of which is the triggering event. We observed that the cationic protein Cyt-c is able to interact electrostatically with the main lipid components of the mitochondrial membranes, the zwitterionic lipids phosphatidylcholine and phosphatidylethanolamine, through mediating phosphate anions that interact specifically with amino groups in the surfaces of the protein and the membrane models. We have investigated the chemical reactivity of Cyt-c associated to model systems and in complexes with PE- and PC-liposomes using a combination of electrochemistry, Raman, fluorescence and mass spectroscopy. In these complexes Cyt-c reacts efficiently with H2O2 at submillimolar levels, which specifically sulphoxides the axial ligand Met80 (SO-Cyt). The modified protein is stable and presents significantly enhanced peroxidatic activity. Based on these results, we postulate that the rise of H2O2 levels from submicromolar to millimolar registered during the initiation of the apoptotic program may represent one signaling event that triggers the gain of peroxidatic function of Cyt-c.