Voltage-gated potassium channel that mediates transmembrane potassium transport in excitable membranes, primarily in the brain, but also in the pancreas and cardiovascular system. Contributes to the regulation of the action potential (AP) repolarization, duration and frequency of repetitive AP firing in neurons, muscle cells and endocrine cells and plays a role in homeostatic attenuation of electrical excitability throughout the brain (PubMed:14684365, PubMed:19383458, PubMed:24494598). Also plays a role in the regulation of exocytosis independently of its electrical function (By similarity). Forms tetrameric potassium-selective channels through which potassium ions pass in accordance with their electrochemical gradient. The channel alternates between opened and closed conformations in response to the voltage difference across the membrane. Homotetrameric channels mediate a delayed-rectifier voltage-dependent outward potassium current that display rapid activation and slow inactivation in response to membrane depolarization (PubMed:22056818). Can form functional homotetrameric and heterotetrameric channels that contain variable proportions of KCNB2; channel properties depend on the type of alpha subunits that are part of the channel (By similarity). Can also form functional heterotetrameric channels with other alpha subunits that are non-conducting when expressed alone, such as KCNF1, KCNG1, KCNG3, KCNG4, KCNH1, KCNH2, KCNS1, KCNS2, KCNS3 and KCNV1, creating a functionally diverse range of channel complexes (By similarity). Heterotetrameric channel activity formed with KCNS3 show increased current amplitude with the threshold for action potential activation shifted towards more negative values in hypoxic-treated pulmonary artery smooth muscle cells (By similarity). Channel properties are also modulated by cytoplasmic ancillary beta subunits, such as AMIGO1, KCNE1, KCNE2 and KCNE3, slowing activation and inactivation rate of the delayed rectifier potassium channels (PubMed:22056818). 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. Major contributor to the delayed-rectifier voltage-gated potassium current in neurons of the central nervous system, sympathetic ganglion neurons, neuroendocrine cells, pancreatic beta cells, cardiomyocytes and smooth muscle (PubMed:10506487, PubMed:12270920, PubMed:17767909, PubMed:23161216, PubMed:24494598). Mediates the major part of the somatodendritic delayed-rectifier potassium current in hippocampal and cortical pyramidal neurons and sympathetic superior cervical ganglion (CGC) neurons that acts to slow down periods of firing, especially during high frequency stimulation (By similarity). Plays a role in the induction of long-term potentiation (LTP) of neuron excitability in the CA3 layer of the hippocampus (PubMed:24494598). Contributes to the regulation of the glucose-induced amplitude and duration of action potentials in pancreatic beta-cells, hence limiting calcium influx and insulin secretion (PubMed:12270920, PubMed:17767909, PubMed:19383458, PubMed:23161216). Plays a role in the regulation of resting membrane potential and contraction in hypoxia-treated pulmonary artery smooth muscle cells (By similarity). May contribute to the regulation of the duration of both the action potential of cardiomyocytes and the heart ventricular repolarization QT interval (PubMed:10506487, PubMed:14684365). Contributes to the pronounced pro-apoptotic potassium current surge during neuronal apoptotic cell death in response to oxidative injury (By similarity). May confer neuroprotection in response to hypoxia/ischemic insults by suppressing pyramidal neurons hyperexcitability in hippocampal and cortical regions (By similarity). Promotes trafficking of KCNG3, KCNH1 and KCNH2 to the cell surface membrane, presumably by forming heterotetrameric channels with these subunits (By similarity). Plays a role in the calcium-dependent recruitment and release of fusion-competent vesicles from the soma of neurons, neuroendocrine and glucose-induced pancreatic beta cells by binding key components of the fusion machinery in a pore-independent manner (By similarity). Inhibited by 42 nM hanatoxin 1 (HaTx1), a spider venom toxin of the tarantula G.spatulata. Inhibited by 100 nM stromatoxin 1 (ScTx1), a spider venom toxin of the tarantula S.calceata (By similarity). Modestly sensitive to millimolar levels of tetraethylammonium (TEA) and 4-aminopyridine (4-AP) (PubMed:2002364, PubMed:10414301, PubMed:15858231). Completely insensitive to toxins such as dendrotoxin (DTX) and charybdotoxin (CTX) (By similarity). 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 more than 20 msec (PubMed:2002364). After that, inactivate very slowly, i.e within more than 5 sec (PubMed:2002364). Their activation requires low threshold potentials at about -20 to -30 mV with a midpoint activation at about 10 mV. For inactivation, the voltage at half-maximal amplitude is about -20 mV. The time constant for recovery after inactivation is about 1.6 sec. Channels have an unitary conductance of about 8 pS. The voltage-dependence of activation and inactivation and other channel characteristics vary depending on the experimental conditions, the expression system, the presence or absence of ancillary subunits and post-translational modifications. Homotetramer or heterotetramer with KCNB2. Heterotetramer with non-conducting channel-forming alpha subunits such as KCNF1, KCNG1, KCNG3, KCNG4, KCNH1, KCNH2, KCNS1, KCNS2, KCNS3 and KCNV1 (By similarity). Channel activity is regulated by association with ancillary beta subunits such as AMIGO1, KCNE1, KCNE2 and KCNE3 (PubMed:22056818). Self-associates (via N-terminus and C-terminus); self-association is required to regulate trafficking, gating and C-terminal phosphorylation-dependent modulation of the channel. Interacts (via C-terminus) with STX1A (via C-terminus); this decreases the rate of channel activation and increases the rate of channel inactivation in pancreatic beta cells, induces also neuronal apoptosis in response to oxidative injury as well as pore-independent enhancement of exocytosis in neuroendocrine cells, chromaffin cells, pancreatic beta cells and from the soma of dorsal root ganglia (DRG) neurons. Interacts (via N-terminus) with SNAP25; this decreases the rate of channel inactivation in pancreatic beta cells and also increases interaction during neuronal apoptosis in a N-methyl-D-aspartate receptor (NMDAR)-dependent manner. Interacts (via N-terminus and C-terminus) with VAMP2 (via N-terminus); stimulates channel inactivation rate. Interacts with CREB1; this promotes channel acetylation in response to stimulation by incretin hormones. Interacts (via N-terminus and C-terminus) with MYL12B. Interacts (via N-terminus) with PIAS3; this increases the number of functional channels at the cell surface. Interacts with SUMO1 (By similarity). Interacts (via phosphorylated form) with PTPRE isoform 2; this reduces phosphorylation and channel activity in heterologous cells (PubMed:10921884). Localizes to high-density somatodendritic clusters and non-clustered sites on the surface of neocortical and hippocampal pyramidal neurons in a cortical actin cytoskeleton-dependent manner (PubMed:24477962). Localizes also to high-density clusters in the axon initial segment (AIS), at ankyrin-G-deficient sites, on the surface of neocortical and hippocampal pyramidal neurons (PubMed:24477962). KCNB1-containing AIS clusters localize either in close apposition to smooth endoplasmic reticulum cisternal organelles or with GABA-A receptor-containing synapses of hippocampal and cortical pyramidal neurons, respectively (PubMed:24477962). Localizes to high-density clusters on the cell surface of atrial and ventricular myocytes and at the lateral plasma membrane in epithelial cells. Localizes both to the axial and transverse tubules (T tubule) and sarcolemma in ventricular myocytes. Associated with lipid raft domains. In cortical neurons, apoptotic injuries induce de novo plasma membrane insertion in a SNARE-dependent manner causing an apoptotic potassium current surge (By similarity). Expressed in the brain (PubMed:17767909, PubMed:22056818). Expressed in the heart (PubMed:14684365). Expressed in pyramidal neurons and interneurons of the hippocampus (PubMed:22056818, PubMed:24494598). Expressed in neocortical pyramidal neurons (PubMed:22056818, PubMed:24477962). Expressed in dorsal root ganglia (DRG) neurons (PubMed:19357235). Expressed in pancreatic beta cells (PubMed:12270920, PubMed:17767909). Expressed in Schwann cells (PubMed:10921884). Expressed in ventricular myocytes (at protein level) (PubMed:14684365, PubMed:10506487). 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. The N-terminal and C-terminal cytoplasmic regions mediate homooligomerization; self-association is required to regulate trafficking, gating and C-terminal phosphorylation-dependent modulation of the channel (By similarity). The N-terminal cytoplasmic region is important for interaction with other channel-forming alpha subunits and with ancillary beta subunits (PubMed:22056818). The C-terminus is necessary and sufficient for the restricted localization to, and clustering within, both in soma and proximal portions of dendrite of neurons and in lateral membrane of non-neuronal polarized cells. The C-terminus is both necessary and sufficient as a mediator of cholinergic and calcium-stimulated modulation of channel cell membrane clustering localization and activity in hippocampal neurons (By similarity). Phosphorylated. Differential C-terminal phosphorylation on a subset of serines allows graded activity-dependent regulation of channel gating in hippocampal neurons. Ser-607 and Tyr-128 are significant sites of voltage-gated regulation through phosphorylation/dephosphorylation activities. Tyr-128 can be phosphorylated by Src and dephosphorylated by cytoplasmic form of the phosphatase PTPRE. CDK5-induced Ser-607 phosphorylation increases in response to acute blockade of neuronal activity. Phosphorylated on Tyr-128 by Src and on Ser-804 by MAPK14/P38MAPK; phosphorylations are necessary and sufficient for an increase in plasma membrane insertion, apoptotic potassium current surge and completion of the neuronal cell death program. Phosphorylated on Ser-520, Ser-655, Ser-607 and Ser-804 by CDK5; phosphorylation is necessary for KCNB1 channel clustering formation. The Ser-607 phosphorylation state differs between KCNB1-containing clusters on the proximal and distal portions of the axon initial segment (AIS). Highly phosphorylated on serine residues in the C-terminal cytoplasmic tail in resting neurons. Phosphorylated in pancreatic beta cells in response to incretin hormones stimulation in a PKA- and RPS6KA5/MSK1-dependent signaling pathway, promoting beta cell survival. Phosphorylation on Ser-567 is reduced during postnatal development with low levels at P2 and P5; levels then increase to reach adult levels by P14. Phosphorylation on Ser-457, Ser-541, Ser-567, Ser-607, Ser-655 and Ser-719 as well as the N-terminal Ser-15 are sensitive to calcineurin-mediated dephosphorylation contributing to the modulation of the voltage-dependent gating properties. Dephosphorylation by phosphatase PTPRE confers neuroprotection by its inhibitory influence on the neuronal apoptotic potassium current surge in a Zn(2+)-dependent manner. Dephosphorylated at Ser-607 by protein phosphatase PPP1CA. Hypoxia-, seizure- or glutamate-induced neuronal activities promote calcium/calcineurin-dependent dephosphorylation resulting in a loss of KCNB1-containing clustering and enhanced channel activity. In response to brain ischemia, Ser-567 and Ser-607 are strongly dephosphorylated while Ser-457 and Ser-719 are less dephosphorylated. In response to brain seizures, phosphorylation levels on Ser-567 and Ser-607 are greatly reduced (By similarity). Phosphorylated/dephosphorylated by Src or FYN tyrosine-protein kinases and tyrosine phosphatase PTPRE in primary Schwann cells and sciatic nerve tissue (PubMed:10921884). Acetylated. Acetylation occurs in pancreatic beta cells in response to stimulation by incretin hormones in a histone acetyltransferase (HAT)/histone deacetylase (HDAC)-dependent signaling pathway, promoting beta cell survival. Sumoylated on Lys-474, preferentially with SUMO1; sumoylation induces a positive shift in the voltage-dependence of activation and inhibits channel activity. Sumoylation increases the frequency of repetitive action potential firing at the cell surface of hippocampal neurons and decreases its frequency in pancreatic beta cells. Desumoylated by SENP1. Mice show normal motor coordination and visual acuity, but are hyperactive, exhibit defects in spatial learning ability and show reduced anxiety-like behavior (PubMed:24494598). Show a higher incidence and a shorter latency to seizure progression compared to wild-type mice (PubMed:24494598). Display reduced fasting blood glucose levels and elevated serum insulin levels (PubMed:17767909, PubMed:19383458). Glucose tolerance and insulin secretion is enhanced compared to control animals (PubMed:17767909, PubMed:19383458). Show impaired long-term potentiation in hippocampal neurons (PubMed:24494598). Display a reduction in the slowly deactivating delayed rectifier potassium current in hippocampal pyramidal neurons (PubMed:24494598). Glucose-induced action potential (AP) duration and amplitude is increased while the firing frequency is reduced in pancreatic beta cells (PubMed:17767909, PubMed:19383458). Belongs to the potassium channel family. B (Shab) (TC 1.A.1.2) subfamily. Kv2.1/KCNB1 sub-subfamily.