The in vitro characterization of membrane proteins, and their interactions with other molecules, is critical to drug discovery. One of the largest roadblocks to these studies is the isolation of a protein of interest in its native conformational state within a membrane-mimetic environment. Micelles have traditionally served, and remain, as one of the primary systems for the formation of such so-called protein-detergent complexes (PDCs). Despite the vast number of surfactants that have been newly developed for PDCs, design rules for their selection and formulation to optimize protein stability and activity are lacking. This talk will provide a historical perspective on success in this area, and highlight some of our recent progress in developing rational design criteria for PDCs. Specifically, we report results of studies on PDCs containing non-ionic surfactants with added sterol derivatives, and their influence on the conformational stability of a human G-protein coupled receptor, hA2aR. Combining detailed biophysical and microstructural studies on various PDCs reveals critical, quantitative parameters of micellar systems which can be used to optimize their formulation for a membrane protein of interest. Specifically, we find that optimal ligand binding activity of hA2aR (a critical reporter of conformational stability) is strongly correlated with morphologies and sterol content which approximate those of the native mammalian cell membrane. This result, though seemingly intuitive, highlights the importance of aggregate structure over simple molecular chemistry in determining the success of micelle-based PDCs.

Toward rational design of protein-detergent complexes for in vitro membrane protein characterization

245th National Meeting (2013)

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