Voltage-gated potassium channel that mediates transmembrane potassium transport in excitable membranes. The channel alternates between opened and closed conformations in response to the voltage difference across the membrane. Forms rapidly inactivating tetrameric potassium-selective channels through which potassium ions pass in accordance with their electrochemical gradient and may contribute to A-type currents (PubMed:2448636). Plays a role in the regulation of sleep need or efficiency (PubMed:15858564). Plays a role in sexual behavior, where it is important for male sex discrimination (PubMed:22292044). Homotetramer or heterotetramer of potassium channel proteins. The transmembrane segment S4 functions as voltage-sensor and is characterized by a series of positively charged amino acids at every third position. Channel opening and closing is effected by a conformation change that affects the position and orientation of the voltage-sensor paddle formed by S3 and S4 within the membrane. A transmembrane electric field that is positive inside would push the positively charged S4 segment outwards, thereby opening the pore, while a field that is negative inside would pull the S4 segment inwards and close the pore. Changes in the position and orientation of S4 are then transmitted to the activation gate formed by the inner helix bundle via the S4-S5 linker region. Partially edited. Reduced sleep (PubMed:15858564). Flies sleep for one-third of the wild-type amount (PubMed:15858564). They perform normally in a number of tasks, have preserved sleep homeostasis, but are not impaired by sleep deprivation (PubMed:15858564). They also have a reduced lifespan (PubMed:15858564). Males are able to discriminate between males and females during courtship but their courtship of females is reduced, suggesting that their perception and/or response to wild-type female pheromones is decreased (PubMed:22292044). RNAi-mediated knockdown in all neurons or specifically in the mushroom bodies of adult males, impairs their ability to discriminate between males and females (PubMed:22292044). However, knockdown in various chemosensory peripheral neurons has no effect on male sex discrimination (PubMed:22292044). Belongs to the potassium channel family. A (Shaker) (TC 1.A.1.2) subfamily. Shaker sub-subfamily.