Voltage-gated K+ channels in the plasma membrane control the repolarization and the frequency of action potentials in neurons, muscles and other excitable cells. The KV gene family encodes more than 30 proteins that comprise the subunits of the K+ channels, and they vary in their gating and permeation properties, subcellular distribution and expression patterns. Functional KV channels assemble as tetramers consisting of pore-forming ?subunits (KV), which include the KV1, KV2, KV3, KV4 and KV9 proteins, and accessory or KV-subunits that modify the gating properties of the coexpressed KV subunits. KV9.2 is a K+ channel subunit that reduces the ion flow and regulates channel activity. It localizes to the cell membrane and, in the absence of KCNB1, KV9.2 may not reach the plasma membrane and may remain in an intracellular compartment.