Cannabinoid photolabelling of a G-protein gamma-subunit in mouse peritoneal cells.

Binding and photoactivation of a cannabinoid-derived ligand to intact mouse peritoneal cells has resulted in the labelling of a G-protein gamma-subunit. The assignment of structure is based on the product's physical characteristics and its ability to react with a polyclonal antiserum raised against the partial amino acid sequence for a gamma-subunit expressed in spleen cells. The binding characteristics of the ligand to the cells suggests that this gamma-subunit, and its associated alpha and beta subunits, are located in close proximity to one of the transmembrane cannabinoid receptors. Our findings further suggest a possible experimental approach to identifying receptor-G-protein complexes in intact cells.