The following text describes a protein:
Function:
Voltage-gated potassium channel that mediates transmembrane potassium transport in excitable membranes, primarily in the brain and central nervous system. Prevents aberrant action potential firing and regulates neuronal output. 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. Can form functional homotetrameric channels and heterotetrameric channels with other family members; the channels characteristics depend critically on the types of channel-forming alpha subunits that are present (By similarity). Channel properties are modulated by cytoplasmic beta subunits that regulate the subcellular location of the alpha subunits (By similarity). 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. Homotetrameric KCNA2 forms a delayed-rectifier potassium channel that opens in response to membrane depolarization, followed by slow spontaneous channel closure. Regulates neuronal excitability and plays a role as pacemaker in the regulation of neuronal action potentials (By similarity). KCNA2-containing channels play a presynaptic role and prevent hyperexcitability and aberrant action potential firing (By similarity). Response to toxins that are selective for KCNA2-containing potassium channels suggests that in Purkinje cells, dendritic subthreshold KCNA2-containing potassium channels prevent random spontaneous calcium spikes, suppressing dendritic hyperexcitability without hindering the generation of somatic action potentials, and thereby play an important role in motor coordination (By similarity). Plays a role in the induction of long-term potentiation of neuron excitability in the CA3 layer of the hippocampus (By similarity).
Subcellular Localization:
Cell membrane; Multi-pass membrane protein.
Domain:
The cytoplasmic N-terminus is important for tetramerization. Interactions between the different subunits modulate the gating characteristics (By similarity); The transmembrane segment S4 functions as a 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.
Sequence:
MTVATGDLTDGSVGFAGHPQDSYDPEPDHECCERVVINISGLRFETQLKTLSQFPETLLGDPKKRMRYFDPLRNEYFFDRNRPSFDAILYFYQSGGRLRRPVNVPLDIFSEEIRFYELGEEAMEIFREDEGFIKEEERPLPDNEFQKQVWLLFEYPESSGPARIIAIISVTVILISIVSFCLETLPVFRDENEDMHGSGGNYYSYPNSTVRFQKSNTFTDPFFIVETLCIIWFSFEFLVRFLACPSKAVFFTNLMNIIDIVAIIPYFITLGTELAEKTEDGQQGQQAMSLAILRVIRLVRVFRIFKLSRHSKGLQILGQTLNASMRELGLLIFFLFIGVILFSSAVFFAEADERDSQFPSIPDAFWWAVVSMTTVGYGDMVPTTIGGKIVGSLCAIAGVLTIALPVPVIVSNFNYFYHRETEGEEQAQYLQVTSCPKIPSSPDLQKSRSASTLSKSDYMEIQEGVNHSNEDFREKNLKTANCTLGNTNYVNITKMLTDV