Two-pore potassium channel modulating the proton motive force (pmf) necessary to convert photochemical energy into physiological functions. Mediates the potassium efflux from the thylakoid lumen required for the regulation of the transmembrane electrical potential, the enhancement of the pH gradient for ATP synthesis, the regulation of electron flow, and pH-mediated photoprotective responses. Requires calcium for channel activity. Inhibited by barium, but not by tetraethylammonium. Homodimer. PubMed:24009357 shows a thylakoid location instead of the tonoplast location previously described. Expressed in roots, stems, hypocotyls, leaves and flowers. Detected in root tips and in mesophyll cells and guard cells of the leaves. 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. The C-terminus is not required for transport to the vacuolar membrane. RNAi-mediated knockdown of the protein causes no effects on germination or on plants grown under normal conditions, but decreases the rosette size, enhances the accumulation of anthocyans and desorganizes the photosynthetic membranes when the plants are grown under high light. Belongs to the two pore domain potassium channel (TC 1.A.1.7) family.