Ciliary membrane vesicles of paramecium contain the voltage-sensitive calcium channel

Calcium influx into ciliary membrane vesicles from paramecia was measured by using arsenazo III as metallochromic indicator and as intravesicular calcium trap. Influx was rapid and reversible. In ciliary membrane vesicles from paramecium pawn mutants which lack the voltage-sensitive calcium channel, calcium influx was significantly less than in wild-type paramecia. These data demonstrate that the voltage-dependent calcium channel of paramecia is functional in a cell-free system and available for biochemical studies.