Calcium-activated potassium channel subunit beta-2 is a protein that in humans is encoded by the KCNMB2gene.12
MaxiK channels are large conductance, voltage and calcium-sensitive potassium channels which are fundamental to the control of smooth muscle tone and neuronal excitability. MaxiK channels can contain two distinct subunits: a pore-forming alpha subunit and a modulatory beta subunit. Each complete MaxiK channel contains four copies of the pore-forming alpha subunit and up to four beta subunits. The protein encoded by the KCNMB2 gene is an auxiliary beta subunit which influences the calcium sensitivity of MaxiK currents and, following activation of MaxiK current, causes persistent inactivation. The subunit encoded by the KCNMB2 gene is expressed in various endocrine cells, including pancreas and adrenal chromaffin cells. It is also found in the brain, including the hippocampus. The KCNMB2 gene is homologous to three other genes found in mammalian genomes: KCNMB1 (found primarily in smooth muscle), KCNMB3, and KCNMB4 (the primary brain MaxiK auxiliary subunit).2
Calcium-activated potassium channel subunit beta-2 comprises two domains. An N-terminalcytoplasmic domain, the ball and chain domain, which is responsible for the fast inactivation of these channels,3 and a C-terminal calcium-activated potassium channel beta subunit domain. The N-terminal domain only occurs in calcium-activated potassium channel subunit beta-2, while the C-terminal domain is found in related proteins.
^Bentrop D, Beyermann M, Wissmann R, Fakler B (November 2001). "NMR structure of the "ball-and-chain" domain of KCNMB2, the beta 2-subunit of large conductance Ca2+- and voltage-activated potassium channels". J. Biol. Chem.276 (45): 42116–21. doi:10.1074/jbc.M107118200. PMID11517232.
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Brenner R, Jegla TJ, Wickenden A, et al. (2000). "Cloning and functional characterization of novel large conductance calcium-activated potassium channel beta subunits, hKCNMB3 and hKCNMB4". J. Biol. Chem.275 (9): 6453–61. doi:10.1074/jbc.275.9.6453. PMID10692449.
Uebele VN, Lagrutta A, Wade T, et al. (2000). "Cloning and functional expression of two families of beta-subunits of the large conductance calcium-activated K+ channel". J. Biol. Chem.275 (30): 23211–8. doi:10.1074/jbc.M910187199. PMID10766764.
Bentrop D, Beyermann M, Wissmann R, Fakler B (2001). "NMR structure of the "ball-and-chain" domain of KCNMB2, the beta 2-subunit of large conductance Ca2+- and voltage-activated potassium channels". J. Biol. Chem.276 (45): 42116–21. doi:10.1074/jbc.M107118200. PMID11517232.
Hartness ME, Brazier SP, Peers C, et al. (2004). "Post-transcriptional control of human maxiK potassium channel activity and acute oxygen sensitivity by chronic hypoxia". J. Biol. Chem.278 (51): 51422–32. doi:10.1074/jbc.M309463200. PMID14522958.
Zeng XH, Benzinger GR, Xia XM, Lingle CJ (2007). "BK channels with beta3a subunits generate use-dependent slow afterhyperpolarizing currents by an inactivation-coupled mechanism". J. Neurosci.27 (17): 4707–15. doi:10.1523/JNEUROSCI.0758-07.2007. PMID17460083.
Zarei MM, Song M, Wilson RJ, et al. (2007). "Endocytic trafficking signals in KCNMB2 regulate surface expression of a large conductance voltage and Ca(2+)-activated K+ channel". Neuroscience147 (1): 80–9. doi:10.1016/j.neuroscience.2007.04.019. PMID17521822.