Constructing ion channels from water-soluble α-helical barrels

Area of Science:

• Biophysical chemistry
• Structural biology
• Membrane biophysics

Background:

• Designing self-assembling peptides into functional membrane ion channels presents significant challenges.
• Simultaneous control over inter-peptide hydrophobic interactions and peptide-lipid interface interactions is crucial.

Purpose of the Study:

• To rationally design and characterize novel alpha-helical peptide barrels capable of forming functional ion channels in lipid bilayers.
• To investigate the structural dynamics and conformational changes of designed peptides within a membrane environment.

Main Methods:

• Rational de novo design of water-soluble alpha-helical barrels with polar interiors.
• High-resolution X-ray crystallography for structural confirmation.
• Single-channel electrical recordings and fluorescent imaging in lipid bilayers.
• X-ray crystallography in lipidic cubic phase and computational analyses.

Main Results:

• Successfully designed and structurally confirmed alpha-helical barrels with water-filled lumens.
• Demonstrated formation of monodisperse, cation-selective ion channels with unitary conductance in membranes.
• Identified an alternative, constricted channel state via X-ray crystallography in lipidic cubic phase.
• Computational analyses provided insights into the properties of different peptide states.

Conclusions:

• The designed peptides can self-assemble into functional cation-selective ion channels in lipid bilayers.
• Peptides can adopt distinct conformational states within the membrane, impacting channel function.
• This multi-step design and characterization approach advances the field of artificial ion channel engineering.