Voltage-independent, instantaneously activating, potassium-selective plasma membrane ion channel. Open rectifier. Regulated by cytoplasmic pH and extra-cellular calcium. Has some permeability for Rb(+) and NH(4)(+), but none for Na(+) or Li(+). Homodimer. Predominantly expressed in pollen. Not expressed during very early stages of flower development, but detected when buds are still closed. Each of the two pore-forming region (also called P-domain or P-loop) is enclosed by two transmembrane segments (2P/4TM) and contains the GYGD signature motif which seems to be involved in potassium selectivity. No effect on pollen germination rate and growth. Belongs to the two pore domain potassium channel (TC 1.A.1.7) family.