Voltage-gated potassium channel that mediates transmembrane potassium transport in excitable membranes, primarily in the brain and smooth muscle cells. Channels open or close in response to the voltage difference across the membrane, letting potassium ions pass in accordance with their electrochemical gradient. Homotetrameric channels mediate a delayed-rectifier voltage-dependent outward potassium current that display rapid activation and slow inactivation in response to membrane depolarization. Can form functional homotetrameric and heterotetrameric channels that contain variable proportions of KCNB1; channel properties depend on the type of alpha subunits that are part of the channel. Can also form functional heterotetrameric channels with other alpha subunits that are non-conducting when expressed alone, such as KCNS1 and KCNS2, creating a functionally diverse range of channel complexes. In vivo, membranes probably contain a mixture of heteromeric potassium channel complexes, making it difficult to assign currents observed in intact tissues to any particular potassium channel family member. Contributes to the delayed-rectifier voltage-gated potassium current in cortical pyramidal neurons and smooth muscle cells. Inhibited by quinine at micromolar levels. Modestly sensitive to millimolar levels of tetraethylammonium (TEA) and 4-aminopyridine (4-AP). Homotetrameric channels expressed in xenopus oocytes or in mammalian non-neuronal cells display delayed-rectifier voltage-dependent potassium currents which are activated during membrane depolarization, i.e within a risetime of about 20 msec. After that, inactivate very slowly. Their activation requires low threshold potentials of about -20 to -30 mV, with a midpoint activation at about 10 mV. For inactivation, the voltage at half-maximal amplitude is about -30 mV. Channels have an unitary conductance of about 14 pS. The voltage-dependence of activation and inactivation and other channel characteristics vary depending on the experimental conditions, the expression system and post-translational modifications. Homotetramer or heterotetramer with KCNB1. Heterotetramer with KCNS1 and KCNS2. Localized uniformly throughout cell bodies and dendrites. Colocalizes with KCNB1 to high-density somatodendritic clusters on cortical pyramidal neurons. 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. Phosphorylated. Belongs to the potassium channel family. B (Shab) (TC 1.A.1.2) subfamily. Kv2.2/KCNB2 sub-subfamily.