Highly selective outward-rectifying potassium channel. Involved in potassium release into the xylem sap toward the shoots. Assuming opened or closed conformations in response to the voltage difference across the membrane, the channel is activated by depolarization. The voltage-dependence of the channel is abolished by internal or external acidification. May interact with the cytoskeleton or with regulatory proteins. The potassium channel is probably composed of a homo- or heterotetrameric complex of pore-forming subunits. Expressed in root pericycle and xylem parenchyma, and in flower at a lower level. In roots, strongly inhibited by 2,4-dichlorophenoxyacetic acid (2,4-D), abscisic acid (ABA) and benzyladenine (BA) treatment or by potassium starvation. The segment S4 is probably the voltage-sensor and is characterized by a series of positively charged amino acids. The pore-forming region H5 is enclosed by the transmembrane segments S5 and S6 in the Shaker-type (1P/6TM) and contains the GYGD signature motif which seems to be involved in potassium selectivity. The KHA domain (rich in hydrophobic and acidic residues) present in the C-terminal part is likely to be important for tetramerization. Loss-of-function mutation skor-1 leads to a reduced shoot potassium content. Belongs to the potassium channel family. Plant (TC 1.A.1.4) subfamily.