| upon an increase in [Ca2 ]i, KCa channels give rise to an efflux of potassium which via re/hyperpolarization of the membrane potential feeds back onto [Ca2 ]i by limiting calcium influx either through deactivation of voltage-gated calcium (Cav) channels or through increased transport activity of Na+ /Ca2+ exchangers. Accordingly, KCa channels shape the amplitude and duration of calcium transients and thus affect the downstream signaling pathways that are triggered by changes in [Ca2]i (Berkefeld et al., 2010 and references therein). |
KCa are classified into two types, the large conductance (BKCa channels), and the smaller conductance (SKCa channels). Both are homotetramers and both contain an integral membrane domain. The BKCa and SKCa channels, however, show very little sequence homology, and they have evolved unique intracellular sequences to permit calcium sensing (Cox, 2011 ).
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Figure 1: Membrane topology of BKCa channel, α subunit (Cox, 2011 published in BMB Reports and licensed under Creative Commons. )