The voltage-gated Ca2+ release channel in the vacuolar membrane of sugar beet resides in two activity states.

The voltage-gated Ca2+ release channel in the vacuolar membrane of sugar beet tap roots resides in two states which show similar reversal potentials in biionic conditions but differ dramatically in their single channel current and open frequency. State I has a unitary Ca2+ conductance of 3.9 +/- 0.5 pS and channel openings are rare at vacuolar resting potentials. After spontaneous and reversible transition into State II the unitary Ca2+ conductance increases three-fold, accompanied by a concomitant rise in channel activity over the physiological voltage range. The 15- to 19-fold increase in total Ca2+ current after the State I to State II transition could play an essential role in channel activation during signal transduction.