Structural models of Na+, Ca2+, and K+ channels

Area of Science:

• * Biophysics
• * Structural Biology
• * Molecular Biology

Background:

• * Voltage-gated channels are crucial for cellular electrophysiology.
• * Determining their precise structure is complex and iterative.
• * Molecular modeling combined with mutagenesis offers a powerful approach.

Purpose of the Study:

• * To present an iterative process for voltage-gated channel structure determination.
• * To highlight how experimental data refines molecular models.
• * To identify key residues and structural motifs involved in ion selectivity and pore architecture.

Main Methods:

• * Iterative cycles of molecular modeling and mutagenesis experiments.
• * Analysis of ion selectivity for Na+, Ca2+, and K+ channels.
• * Investigating the role of specific residues (e.g., P segment residues) and structural elements (e.g., helices, carbonyl oxygens).
• * Utilizing toxin binding data (e.g., CTX, conotoxins) to model pore vestibules.

Main Results:

• * Experimental confirmation of the P segment forming the ion-selective part of the channel.
• * Identification of residues responsible for Na+ and Ca2+ selectivity.
• * Prediction that carbonyl oxygens of the Gly-Tyr-Gly backbone, not side chains, form the K+ channel selectivity filter.
• * Refined models of the P segment incorporating extracellular toxin binding data and residue accessibility.

Conclusions:

• * Molecular modeling and mutagenesis are effective, albeit evolving, tools for voltage-gated channel structure elucidation.
• * The P segment and specific residues play critical roles in ion selectivity and pore formation.
• * Future advancements in theoretical and experimental methods will further enhance structure determination.