Dynamic interplay between lateral diffusion and conformational states in a secondary transporter revealed by...

Area of Science:

• Biophysics
• Membrane Protein Dynamics
• Nanotechnology

Background:

• Membrane protein function is intrinsically linked to their dynamic structural behavior and interaction with the lipid bilayer.
• Understanding these dynamics is essential for both fundamental biological insights and potential nanotechnological applications.

Purpose of the Study:

• To directly visualize the real-time lateral motion and conformational changes of lactose permease (LacY).
• To investigate the influence of substrate binding and electrochemical gradients on LacY dynamics and membrane mechanics.
• To establish a mechanistic framework for studying secondary transporters in native-like membrane environments.

Main Methods:

• High-speed atomic force microscopy (HS-AFM) was employed to observe LacY reconstituted into proteolipid sheets.
• Lateral diffusion of LacY dimers was quantified.
• The effects of lactose and ionophores (valinomycin, nigericin) on LacY nanomechanics and morphology were analyzed.

Main Results:

• LacY dimers exhibit lateral diffusion with an average velocity of ~3 nm/s and a diffusion coefficient of ~18 nm²/s.
• Lactose and ionophores induced distinct nanomechanical and morphological changes in LacY.
• A strong coupling was observed between electrochemical gradients, membrane mechanics, and LacY conformational states.

Conclusions:

• Protein lateral mobility and mechanical feedback from the membrane dynamically modulate transport efficiency.
• Secondary transporter function is influenced by dynamic interactions within the native-like membrane environment.
• HS-AFM is a powerful tool for resolving nanoscale dynamics in complex membrane systems.