Refinement of a cryo-EM structure of hERG: Bridging structure and function.

Area of Science:

• Structural Biology
• Molecular Physiology
• Cardiovascular Science

Background:

• The human ether-a-go-go-related gene (hERG) encodes the Kv11.1 potassium channel, crucial for cardiac action potential repolarization.
• A high-resolution cryo-EM structure exists for the open hERG channel, but it lacks key functional interactions identified previously.
• Discrepancies between structural data and functional studies hinder a complete understanding of hERG channel mechanisms.

Purpose of the Study:

• To refine the existing cryo-EM structure of the hERG channel in its open state.
• To identify and validate functionally important interactions, specifically salt bridges, within the hERG voltage-sensing domain.
• To reconcile structural information with electrophysiology and biochemical data for a comprehensive understanding of hERG channel function.

Main Methods:

• Molecular Dynamics Flexible Fitting (MDFF) was employed to refine the cryo-EM structure of the hERG channel.
• Computational refinement focused on recovering functionally relevant salt bridges in the depolarized state.
• Electrophysiology experiments were conducted to validate the functional significance of newly predicted salt bridges.

Main Results:

• MDFF refinement successfully recovered missing, functionally important salt bridges in the depolarized hERG structure.
• A novel salt bridge, predicted by the refinement protocol, was functionally validated through electrophysiology.
• The refined structure provides a more accurate representation of hERG channel interactions in its open state.

Conclusions:

• Refinement of cryo-EM structures using computational methods like MDFF can bridge the gap between structural data and functional insights.
• The identified and validated salt bridges are critical for understanding hERG channel gating and function.
• This study enhances our structural and functional understanding of the hERG channel's voltage-sensing domain.