Solubilization of endothelin receptors from bovine lung plasma membranes in a non-aggregated state and estimation of their minimal functional sizes.

Bovine lung endothelin receptors were solubilized in a non-aggregated state and characterized in terms of their minimal functional size and chemical nature of the ligand-binding site. A variety of detergents and their combinations were tested for their efficiency to solubilize endothelin receptors from bovine lung plasma membranes, and a combination of 0.4% digitonin and 0.25% CHAPS was found to be very effective in obtaining highly dispersed receptor solution. Gel filtration of the CHAPS/digitonin-solubilized receptors revealed the presence of two receptor species eluting at the positions corresponding to 34 and 52 kDa. These values were in good agreement with those estimated by affinity labeling and SDS-polyacrylamide gel electrophoresis, establishing that they represent minimal functional units. Chemical modification of ligand-occupied and free receptors with p-chloromercuriphenylsulfonic acid revealed that both 34 and 52 kDa receptors have SH group(s) essential for the receptor activity in their ligand-binding sites.