Molecular Determinants of BK Channel Functional Diversity and Functioning

Area of Science:

• Physiology
• Molecular Biology
• Biophysics

Background:

• Large-conductance Ca2+- and voltage-activated K+ (BK) channels are crucial for smooth muscle tone, hearing, and neurosecretion.
• These channels are tetramers formed by the pore-forming α subunit (encoded by KCNMA1).
• BK channels are implicated in various channelopathies.

Purpose of the Study:

• To review the physiological importance of BK channels.
• To discuss the allosteric mechanisms of BK channel activation, linking models to structure.
• To explain the unique conductance and selectivity properties of BK channels.

Main Methods:

• Review of existing literature on BK channel physiology, structure, and function.
• Analysis of allosteric models for channel activation.
• Examination of studies using ions, blockers, and toxins to probe conduction and gating.

Main Results:

• BK channels exhibit modular structures with allosteric communication between voltage sensors, Ca2+ binding sites, and pore gates.
• Paradoxical large conductance and K+ selectivity are explained through structural insights.
• The gating ring, composed of COOH termini, houses voltage sensors and Ca2+ binding sites.

Conclusions:

• BK channel diversity arises from alternative splicing of the KCNMA1 gene and association with modulatory β and γ subunits.
• These associations significantly alter BK channel phenotype and pharmacology.
• Understanding BK channel regulation is key to addressing channelopathies.