Probing the Dimerization of Transmembrane Helices in Lipid Bilayers

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AbstractMCB 0315663Biophysical studies of membrane protein dimerization, one of the basic steps in folding and signal transduction, are hindered by the lack of an adequate method to probe dimerization in a model bilayer environment. In this project, the PI will develop a new tool for probing membrane protein dimerization in a lipid bilayer. She will measure the thermodynamics of Glycophorin A dimerization in a lipid environment, and compare the results to previous studies in detergent systems. The method to be developed requires the assembly of surface-attached bilayers containing laterally mobile membrane proteins with identical orientations. The dimerization of the fluorescently labeled proteins will be measured using imaging resonance energy transfer. This project will yield thermodynamic measurements of GpA dimerization in a bilayer environment. In the long term, the method will be a new useful tool in dissecting the chemistry of interactions within membrane proteins in hydrophobic environments. Approximately 20% of all proteins in complex organisms are membrane-associated. Despite their abundance and key roles in cell life, our knowledge of the folding and the structure-function relationship for membrane proteins is limited, and lags far behind that of soluble proteins. In part, this is due to limited biophysical tools to adequately probe the physical-chemical principles underlying membrane protein function. For instance, a method to probe the dimerization of transmembrane helices in the native-like lipid bilayer environment is still missing. In this project, the PI will develop such a method by assembling surface grafted lipid bilayers that contain membrane proteins. Dimerization will be measured using an imaging fluorescence technique. The PI will train two graduate students and enhance the educational experience of underrepresented minority students currently conducting research in her laboratory.