Defective guanyl nucleotide-binding protein beta-gamma subunits in a forskolin-resistant mutant of the Y1 adrenocortical cell line

Analysis of forskolin-resistant mutants of a Y1 mouse adrenocortical tumor cell line showed that it is completely insensitive to corticotropin, fully responsive to NaF and contains decreased levels of GTP-binding protein G protein. The functional activities of the G protein beta-gamma subunits in both mutant and wild type Y1 cell membranes were investigated. The results showed that the mutant G proteins contain altered beta-gamma subunits which are functionally deficient in facilitating pertusis toxin-mediated ADP ribosylation of G(sub t-alpha), as well as rhodopsin-catalyzed guanine nucleotide exchange on G(sub t-alpha).