Systematic Perturbations of Micelle Properties to Investigate the Stabilization of Membrane Protein Structure and Function

Abstract

Membrane protein research is hampered by the difficulty in selecting a membrane mimic that solubilizes and stabilizes protein fold and function. While detergents are often utilized, identifying the appropriate detergent composition to maintain protein solubilization and stability is an expensive, time-consuming, empirical process that is often unsuccessful. The goal of this research is to understand the interactions between detergent and protein by relating physical surfactant properties with membrane protein fold, function, and stability, enabling rational detergent selection. To determine important micelle and protein characteristics, outer membrane phospholipase A1 (OMPLA), the protease OmpT, and the lipid A palmitoyltransferase PagP were purified in different detergent micelles with varying properties such as alkyl chain length, charge, and head group. The overall protein structure and function were evaluated in many pure micelles to identify trends with detergent characteristics and protein function. Upon determination of kinetic parameters for several β-barrel proteins in pure micelles, protein function and structure will be investigated with mixed micelles, to test hypotheses generated by the trends observed in pure micelles. This research will provide a logical rationale for the selection of detergents based on the physical properties of membrane proteins and detergents.