ANION CHANNELS OF THE INNER MEMBRANE OF MAMMALIAN AND YEAST MITOCHONDRIA

The inner membrane of yeast and mammalian mitochondria has been studie d in situ with a patch clamp electrode. Anion channels were found in b oth cases, although their behavior and regulation are different. In ma mmalian mitochondria, the principal channel is of around 100 pS conduc tance and opens mainly under depolarized membrane potentials, As no ph ysiological compound able to alter its peculiar voltage dependence has yet been found, it is proposed that this channel may serve as a safeg uard mechanism for recharging the mitochondrial membrane potential. Tw o other anion channels, each with a distinct conductance (one of appro x. 45 pS, the second of at least a tenfold higher value) and kinetics are harbored in the yeast inner membrane. Matrix ATP was found to inte ract with both, but with a different mechanism. It is proposed that th e 45 pS channel may be involved in the homeostatic mechanism of mitoch ondrial volume.