Interaction between residues in the Mg2+-binding site regulates BK channel activation

Area of Science:

• Biophysics
• Molecular Biology
• Ion Channel Physiology

Background:

• Large conductance, voltage- and Ca(2+)-activated K(+) (BK) channels are critical regulators of cellular excitability.
• BK channels possess distinct voltage-sensing and Ca(2+) sensing domains, but the interplay between these domains remains incompletely understood.
• Previous work identified a Mg(2+) binding site at the interface of the membrane-spanning and cytosolic domains, influencing channel activation.

Purpose of the Study:

• To investigate the role of interdomain interactions, particularly involving Mg(2+)-coordination residues, in regulating BK channel gating.
• To elucidate the mechanisms by which these interdomain interactions affect channel activation dynamics.
• To explore the contribution of noncovalent interactions to the allosteric gating of BK channels.

Main Methods:

• Site-directed mutagenesis was employed to introduce charge alterations at key interdomain residues (D99, N172, E374, E399).
• Electrophysiological recordings were used to assess the functional consequences of these mutations on BK channel gating.
• Analysis focused on voltage- and Ca(2+)-dependent activation properties.

Main Results:

• A native interdomain interaction between D99 and E374 was identified, impacting BK channel activation.
• Artificial electrostatic interactions engineered between residues 172 and 399 modulated local and distant conformations.
• These interdomain interactions significantly altered both voltage- and Ca(2+)-dependent BK channel activation.

Conclusions:

• Interdomain interactions play a vital role in the allosteric gating mechanisms of BK channels.
• Specific residue interactions at the interface of functional domains are critical for coordinating channel opening.
• Understanding these interactions provides insights into the dynamic regulation of ion channel function.