Structural basis for gating the high-conductance Ca²⁺-activated K⁺ channel

Area of Science:

• Molecular Biology
• Biophysics
• Neuroscience

Background:

• Ion channels are critical for cellular function, with precise gating mechanisms.
• Slo1 K+ channels are key regulators linking intracellular calcium (Ca2+) and membrane excitability.
• Understanding Slo1 channel regulation is vital for deciphering cellular signaling pathways.

Purpose of the Study:

• To elucidate the structural basis of Slo1 K+ channel regulation by Ca2+ and membrane voltage.
• To compare the Ca2+-free and Ca2+-bound structures of the Aplysia californica Slo1 channel.
• To investigate the mechanism by which Ca2+ binding affects channel conformation and gating.

Main Methods:

• X-ray crystallography to determine the structure of Slo1 K+ channels in different Ca2+ states.
• Comparative structural analysis of Ca2+-free and Ca2+-bound Slo1 channels.
• Biochemical and biophysical techniques to analyze conformational changes and functional implications.

Main Results:

• Ca2+ binding at two distinct sites per subunit stabilizes an expanded conformation of the Ca2+ sensor gating ring.
• Conformational changes in the gating ring are transmitted to the channel pore via covalent linkers.
• Direct protein interfaces connect the gating ring and voltage sensors, enabling voltage-dependent regulation of Ca2+ sensing.

Conclusions:

• Ca2+ binding induces significant conformational changes in the Slo1 channel's gating ring.
• These Ca2+-induced changes are coupled to the pore and voltage-sensing domains, integrating multiple regulatory inputs.
• The findings provide a structural framework for understanding how Slo1 channels link intracellular Ca2+ levels and membrane voltage to control K+ flux.