Ion conduction through MscS as determined by electrophysiology and simulation

Area of Science:

• Biophysics
• Molecular Biology
• Membrane Protein Research

Background:

• Mechanosensitive channel of small conductance (MscS) regulates ion release in bacteria under osmotic stress.
• The functional state and voltage-dependent gating of MscS remain incompletely understood.
• Relating crystal structure to electrophysiological function is crucial for MscS research.

Purpose of the Study:

• To investigate the voltage and pressure response of MscS using patch-clamp experiments.
• To determine MscS electrostatics and transport properties via molecular dynamics simulations.
• To reconcile experimental findings with the MscS crystal conformation.

Main Methods:

• Patch-clamp electrophysiology to measure MscS activity under pressure and voltage.
• All-atom molecular dynamics simulations of MscS in a lipid bilayer (224,000 atoms).
• Simulations included biasing electrostatic potentials and analysis of ion conduction.

Main Results:

• MscS exhibits pressure-activated, voltage-inactivated gating with slight anion selectivity and ~1 nS conductance.
• Simulations of MscS in crystal conformation showed low conductance.
• Unrestrained MscS with electrostatic bias increased channel radius and matched experimental conductances, primarily via Cl- ions.

Conclusions:

• MscS gating is influenced by both mechanical and electrical forces.
• Simulations suggest conformational flexibility is key to MscS function.
• The study links MscS electrophysiology and structure, highlighting chloride ion permeation.