Correlation of membrane protein conformational and functional dynamics

Area of Science:

• Biophysics
• Structural Biology
• Membrane Proteins

Background:

• Ion channel gating is crucial for cellular function, involving conformational changes.
• Directly correlating protein dynamics with ion flux at sub-millisecond timescales has been challenging.
• Outer membrane protein G (OmpG) serves as a model for pH-dependent pore gating via loop-6 dynamics.

Purpose of the Study:

• To investigate the sub-millisecond conformational dynamics of OmpG's loop-6.
• To correlate these dynamics with the protein's ion channel gating function.
• To elucidate the pH-dependent mechanisms governing OmpG conformational fluctuations.

Main Methods:

• Single-channel electrophysiology to measure ion flux and functional states.
• High-speed atomic force microscopy height spectroscopy (HS-AFM-HS) to monitor loop-6 dynamics.
• Molecular dynamics (MD) simulations to provide atomistic details and energy landscapes.

Main Results:

• OmpG exhibits rapid interconversion between open and closed states across pH conditions.
• HS-AFM-HS successfully captured sub-millisecond conformational dynamics of loop-6.
• MD simulations revealed atomistic details of pH-dependent loop-6 fluctuations and energy landscapes.

Conclusions:

• HS-AFM-HS enables the study of protein dynamics at the timescale of loop and domain fluctuations.
• The study provides a link between observed conformational changes and ion channel function.
• This work advances the understanding of pH-driven gating mechanisms in membrane proteins.