Mediates the voltage-dependent potassium ion permeability of excitable membranes. Assuming opened or closed conformations in response to the voltage difference across the membrane, the protein forms a potassium-selective channel through which potassium ions may pass in accordance with their electrochemical gradient. Heterotetramer of potassium channel proteins. The segment S4 is probably the voltage-sensor and is characterized by a series of positively charged amino acids at every third position. This channel protein belongs to the delayed rectifier class. Belongs to the potassium channel family. C (Shaw) (TC 1.A.1.2) subfamily. Shaw sub-subfamily.