High-Speed Atomic Force Microscopy Reveals the Dynamic Interplay of Membrane Proteins is Lipid-Modulated.

The solvent of membrane proteins is the membrane lipids in which they are embedded. Therefore, the nature of the lipids that surround membrane proteins impacts their dynamics and interactions. Unfortunately, how membrane proteins dynamically interact is difficult to study, and little is experimentally known how membrane proteins interplay in a membrane at the molecular scale. Herein, high-speed atomic force microscopy (HS-AFM) is used to dynamically image a well-controlled bottom-up system consisting of two aquaporin-fold membrane proteins, pentameric FocA and tetrameric GlpF, that interact in membranes composed of varying amounts of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and lipids. It is found that the lipid environment significantly influences membrane protein mobility and interaction, where increased lipid content reduces protein movement, while DOPC-rich environments promote mobility. Furthermore, the supramolecular structures of the membrane proteins and protomer interactions in clusters are also lipid modulated, where lipids favor specific protein-protein interactions, whereas greater interaction variability is found in DOPC. These findings highlight the role of lipids in regulating protein diffusion and interactions and suggest that lipid-protein interaction energetics play a significant role in controlling membrane protein interactions and supramolecular assembly.