Transmembrane determinants of voltage-gating differences between BK (Slo1) and Slo3 channels

Area of Science:

• Molecular biology
• Ion channel function
• Cellular electrophysiology

Background:

• Voltage-gated potassium channels, including Slo (slowpoke) channels, regulate cellular excitability.
• Slo1 and Slo3 channels, despite similarities, show distinct voltage-gating properties.

Purpose of the Study:

• To identify molecular determinants distinguishing human Slo1 and mouse Slo3 channel voltage-gating.
• To elucidate the structural basis for differences in conductance and activation kinetics.

Main Methods:

• Construction and analysis of Slo1/Slo3 chimeras.
• Site-directed mutagenesis of specific transmembrane segments.
• Electrophysiological recordings to assess channel function.

Main Results:

• The selectivity filter influences Slo3 conductance at negative voltages.
• The S6 transmembrane segment is critical for Slo3 deactivation kinetics.
• S4 and S6 segments affect the Slo3 conductance-voltage relationship slope.
• Multiple transmembrane regions contribute to Slo3 activation requirements.
• Specific Slo1 residues (I233, L302, M304) in S5/S6 segments are key for voltage sensor-pore coupling.

Conclusions:

• Distinct regions, including the selectivity filter and transmembrane segments S4 and S6, dictate Slo1 and Slo3 channel gating differences.
• Specific residues in Slo1's S5/S6 segments are crucial for allosteric gating control.