Micelles and Bicelles as Membrane Mimics for Membrane Protein Characterization

Abstract

Micelles and bicelles are used to isolate membrane proteins for biophysical characterization, functional assays, and high-resolution structure determination. Utilizing these membrane mimics requires an extensive screening process to identify the appropriate amphiphilic environment to stabilize a functional membrane protein. To enable rational mimic selection, the goal of this research is to investigate the structural properties of micelles and bicelles to determine how their physical characteristics can forward membrane protein research. Small angle X-ray scattering and small angle neutron scattering were used to investigate the structure of micelles and bicelles, specifically binary mixtures of detergents and lipids. To determine the impact of membrane mimic structure on protein function, outer membrane phospholipase A1, the protease OmpT, and the lipid A palmitoyltransferase PagP were purified in detergent micelles with varying properties, and the overall protein activity was evaluated. Hypotheses based on the correlations between activity and micelle properties were tested using mixed micelles and bicelles with tunable properties. The information gained from these studies will determine the physical properties important in stabilizing membrane proteins and provide guiding principles for selecting membrane mimics.