Simulating Gas Permeation Through the Central Pore of AQP5

Area of Science:

• Biophysics
• Molecular Biology
• Cellular Physiology

Background:

• Aquaporins (AQPs) are integral membrane proteins primarily known as water channels.
• A hypothesis suggests AQPs may also facilitate the permeation of metabolic gases like O2 and CO2.
• The central pore (CP) within AQP tetramers is a potential pathway for gas transport.

Purpose of the Study:

• To investigate the role of aquaporin-5 (AQP5) in facilitating gas permeation.
• To determine if the central pore (CP) of AQP5 contributes to gas transport across membranes.
• To understand the mechanism and significance of protein-mediated gas transport.

Main Methods:

• Atomistic molecular dynamics (MD) simulations of aquaporin-5 (AQP5).
• Free energy calculations using implicit ligand sampling (ILS).
• Concentration gradient simulations of membrane-embedded AQP5 with CO2.

Main Results:

• Gas molecules favorably partition into the hydrophobic central pore (CP) of AQP5.
• CO2 partitioning within the CP cavity exceeds that of the lipid bilayer core.
• The CP facilitates more gas permeations than the four monomeric pores combined, with a mean residence time of 88.1 ns.

Conclusions:

• Aquaporins (AQPs) can facilitate gas permeation across biological membranes.
• The central pore (CP) is a critical element in AQP-mediated gas transport.
• Understanding this mechanism may reveal therapeutic targets for diseases involving altered gas transport.