The effects of various surfactants on the activity and stability of the human adenosine A3 receptor (A3) were investigated. The receptor was expressed using stably transfected HEK293 cells at a concentration of 44 pmol functional receptor per milligram membrane protein and purified using over 50 different nonionic surfactants. A strong correlation was observed between a surfactant's ability to remove A3 from the membrane and the ability of the surfactant to remove A3 selectively relative to other membrane proteins. The activity of A3 once purified also correlates well with the selectivity of the surfactant used. The effects of varying the surfactant were much stronger than those achieved by including A3 ligands in the purification scheme. Notably, all surfactants that gave high efficiency, selectivity and activity fall within a narrow range of hydrophile-lipophile balance values. This effect may reflect the ability of the surfactant to pack effectively at the hydrophobic transmembrane interface. These findings emphasize the importance of identifying appropriate surfactants for a particular membrane protein, and offer promise for the development of rapid, efficient, and systematic methods to facilitate membrane protein purification.
Bibliographical noteFunding Information:
This publication was made possible by National Institutes of Health grant P20 RR-15588 from the COBRE program of the National Center for Research Resources and National Aeronautics and Space Administration grant NAG8-1830 from the Microgravity Research Program. BWB gratefully acknowledges support through a National Institutes of Health Chemistry-Biology Interface Training Grant (T32 GM-08550) and National Science Foundation IGERT Graduate Fellowship (DGE-0221651).