Large conductance calcium-activated potassium channel (alpha subunit) (BK channel (or BKCa, KCa1.1, Slo1))

The **large conductance calcium-activated potassium channel (BK channel; also called Maxi-K, BKCa, KCa1.1, or Slo1)** is a voltage- and calcium-activated ion channel that enables rapid efflux of potassium ions in response to membrane depolarization and/or increased intracellular calcium levels. Structurally, it comprises four α subunits encoded by the KCNMA1 gene, each with seven transmembrane segments, and may associate with regulatory β and γ subunits, which modulate channel kinetics and pharmacology. BK channels are ubiquitously expressed in neuronal, muscle, and secretory cells, acting as integrators of electrical and calcium signals to regulate processes such as membrane repolarization, neurotransmitter release, smooth muscle tone, and circadian rhythms. Dysfunction or pharmacological targeting of BK channels is implicated in several diseases including hypertension, stroke, epilepsy, certain cancers (notably breast cancer), and overactive bladder, making them significant therapeutic targets under investigation.

Other names

Maxi-K channelBKCa channelSlo1KCa1.1 channelbig potassium channelhigh-conductance calcium-activated potassium channelKCNMA1 (gene encoding the alpha subunit)

Channel blockers inhibit potassium efflux, enhance cellular excitability, affect cell cycle and proliferation (notably in cancer models) Channel activators increase potassium efflux, hyperpolarize membrane, reduce neurotransmitter release, relax smooth muscle, anti-excitotoxic/neuroprotective Peptide toxins block the pore directly (e.g., charybdotoxin, iberiotoxin) Small molecule activators/agonists shift channel activation to more negative voltages or potentiate Ca2+ response