Structural basis of fast N-type inactivation in K_v channels

Area of Science:

• Molecular and Cellular Neuroscience
• Ion Channel Physiology
• Structural Biology

Background:

• Voltage-activated ion channels, including sodium (Na_v) and potassium (K_v) channels, generate action potentials.
• Rapid inactivation of these channels shapes nerve impulses and influences synaptic plasticity.
• The precise mechanism of fast inactivation, particularly pore block versus pore closure, remains debated.

Purpose of the Study:

• To elucidate the molecular mechanism of fast inactivation in the Shaker K_v channel.
• To determine the structural basis of inactivation and its regulation.
• To investigate the role of the N-terminus and external ions in the inactivation process.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to resolve channel structures.
• Mass spectrometry to identify protein modifications.
• Electrophysiology to study channel function and inactivation kinetics.

Main Results:

• Resolved structures of the Shaker K_v channel in a fully inactivated state.
• Identified the N-terminal domain acting as a plug, blocking the internal pore in an extended conformation.
• Demonstrated that N-terminal acetylation and RNA editing regulate inactivation, and external K⁺ destabilizes the inactivated state via conformational changes in the selectivity filter.

Conclusions:

• Established a structural mechanism for fast inactivation in K_v channels involving N-terminal pore plugging.
• Revealed that RNA editing and N-terminal acetylation are key regulators of K_v channel inactivation.
• Provided a framework for understanding inactivation in other voltage-activated channels.