Detergents for Extraction, Purification, and Reconstitution of G Protein-Coupled Membrane Receptors

Abstract

G protein-coupled membrane receptors (GPCR) are, perhaps, the most important signaling molecules for the transfer of external signals to the cell interior. The rhodopsin-like receptors are the largest class of GPCR. They are integral membrane proteins with seven transmembrane helices, including not only receptors for vision, but also receptors for neurotransmitters, chemokines, neuropeptides, cannabinoids, lysolipids, prostaglandins, histamines, and odorants, just to mention a few. A still rather limited number of rhodopsin-like GPCR have been successfully overexpressed in various expression systems, solubilized with the help of detergents, purified in quantities up to milligrams, and reconstituted into lipid bilayers for functional and structural studies. Every one of those steps requires the use of detergents. Detergents are also used for crystallization of GPCR, although this will not be subject of my presentation. All GPCR are known to be highly vulnerable to denaturation while solubilized with detergents. The successful laboratories have spent years optimizing experimental conditions to increase yield of purified GPCR. A significant fraction of this process is identifying proper detergents for work with a particular GPCR. Most of this expertise was gained by trial and error. By now, patterns in the use of detergents have emerged that are applicable to more than one of the GPCR. In my talk, I will present experience gained with rhodopsin and the recombinant, type II cannabinoid receptor at my laboratory, but will also review literature on the use of detergents for other GPCR. I hope that my attempt of summarizing practical observations on GPCR and detergent use will stimulate discussions that eventually lead to a more purposeful selection of detergents in the future.