A cysteine-11 to serine mutant of Gα12impairs activation through the thrombin receptor

Abstract
We have recently reported that Gα12 is acylated with palmitic acid [Veit et al., FEBS Lett. 339 (1994) 160–164]. Here we identify cysteine 11 as the sole palmitoylation site and assess the function of Gα12 palmitoylation after expression of wild type and acylation‐deficient mutant in insect cells. Our experimental approach yielded the following results. (1) Palmitoylation of Gα12 has no influence on the subunit interactions. (2) Palmitoylation promotes membrane binding of Gα12 when this protein is expressed alone. Membrane attachment of the heterotrimer occurs independent of the presence of fatty acids in Gα12. (3) Assays for agonist‐stimulated binding of [35S]GTPγS after expression of the human thrombin receptor (PAR1) along with Gα12 and the βγ subunits revealed a 70% inhibition with the palmitoyl‐deficient mutant.