Dual mode of gating of voltage-dependent anion channel as revealed by phosphorylation

The single-channel electrophysiological properties of the voltage-dependent anion channel (VDAC) of mitochondria from rat liver have been investigated under normal and phosphorylated (with protein kinase A) conditions. Experimental observations show that phosphorylation does not affect the current level and the opening probability in the positive clamping potentials, but leads to lowering of current magnitude and opening probability in the negative clamping potentials. The opening probability versus voltage (V) plot for native VDAC fits a Gaussian function symmetric around V = 0, whereas the same for phosphorylated VDAC fits a linear combination of two Gaussian functions. This indicates that there are two gating modes of VDAC; the negative voltage sensor (gate) undergoes modification due to phosphorylation. (C) 2001 Academic Press.