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. May play a role in the nervous system and in the regulation of beating frequency in pacemaker cells. Heterotetramer of potassium channel proteins (By similarity). Interacts (via C-terminal dendritic targeting motif) with SIDL. Co-expressed with SIDL in the nervous system. The N-terminus may be important in determining the rate of inactivation of the channel while the tail may play a role in modulation of channel activity and/or targeting of the channel to specific subcellular compartments. The segment S4 is probably the voltage-sensor and is characterized by a series of positively charged amino acids at every third position. Belongs to the potassium channel family. D (Shal) (TC 1.A.1.2) subfamily. Shal sub-subfamily.