Department of Molecular Physiology and Biophysics - University of Iowa
Host: Dipali Sashital

"Driving Forces of Protein Assembly in Greasy Membranes"

Why do greasy membrane proteins choose to interact with other greasy proteins, instead of the greasy lipids in the surrounding cell membrane? This is a question that is at the heart of membrane protein folding, conformational stability of ion channels and transporters, and regulation as it occurs within cell membranes. Surprisingly, we know very little about the fundamental physical reasons of why proteins surfaces bind to one another in lipid bilayers, the major reason being a lack of tractable systems that are amenable for study in a lab setting.

Recently, my laboratory has developed a new type of model system to study this question based on the dimerization of the large CLC Cl-/H+ transporter in membranes. Using single-molecule fluorescence microscopy, we have been able to examine the protein stoichiometry in membranes at sub-biological dilutions, observe dissociation of the complex into the monomeric state, and determine the equilibrium dimerization reaction in membranes. With this, we are now investigating the physical reasons why CLCs form thermodynamically stable dimers, dissecting contributions from protein interactions, surface complementarity, lipid bilayer structure and composition.

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