THE VOLTAGE SENSOR OF THE MITOCHONDRIAL PERMEABILITY TRANSITION PORE IS TUNED BY THE OXIDATION-REDUCTION STATE OF VICINAL THIOLS - INCREASE OF THE GATING POTENTIAL BY OXIDANTS AND ITS REVERSAL BY REDUCING AGENTS

Reaction of isolated mitochondria with a variety of agents that lead to oxidation or cross-linking of sulfhydryl groups leads to an increased ''open'' probability of the permeability transition pore, a cyclosporin A-sensitive channel. We have investigated the mechanism by which the pore is induced by menadione, diamide, arsenite, and tert-butylhydroperoxide. We find that these inducers increase the probability of pore opening by shifting its gating potential to higher values. Furthermore, the induced shift was prevented by treatment with N-ethylmaleimide or dithiothreitol. At moderate levels of depolarization an apparent I-50 for N-ethylmaleimide of about 5 mu M can be defined, while the N-ethylmaleimide or dithiothreitol effects are overcome by maximal depolarization. We conclude that the oxidation-reduction state of vicinal thiols in cysteinyl residues plays a critical role in tuning the voltage sensor of the transition pore, with an increase of gating potential (i.e. an increase in the probability of pore opening despite a high transmembrane potential difference) as the couple is poised to a more oxidized state. These findings may have implications for the mechanism of cell damage under oxidative stress.