Voltage-independent, large conductance and potassium- selective tonoplast ion channel. Regulated by cytoplasmic calcium and pH. Does not mediate slow-vacuolar (SV) ionic currents, but essential to establish VK currents. Has some permeability for Rb(+) and NH(4)(+), but none for Na(+), Cs(+) or Li(+). Involved in intracellular K(+) redistribution and/or K(+) retranslocation between different tissues.