STIMULATION OF PHOSPHOLIPASE C-BETA(2) BY RECOMBINANT GUANINE-NUCLEOTIDE-BINDING PROTEIN BETA-GAMMA DIMERS PRODUCED IN A BACULOVIRUS INSECTCELL EXPRESSION SYSTEM - REQUIREMENT OF GAMMA-SUBUNIT ISOPRENYLATION FOR STIMULATION OF PHOSPHOLIPASE-C/

Recombinant wild-type beta(1) gamma(1) dimers of signal-transducing gu anine nucleotide-binding proteins (G proteins) and beta(1) gamma 1 dim ers carrying a mutation known to block gamma-subunit isoprenylation (b eta(1) gamma(1)C71S) were expressed in baculovirus-infected insect cel ls. Both wild-type and mutant beta(1) gamma(1) dimers were found in so luble fractions of infected cells upon subcellular fractionation. Anio n exchange chromatographic and metabolic-radiolabeling studies reveale d that the soluble beta(1) gamma(1) preparation contained approximatel y equal amounts of non-isoprenylated and isoprenylated beta(1) gamma(1 ) dimers. Soluble wild-type and mutant beta(1) gamma(1) dimers and nat ive beta(1) gamma(1) dimers purified from bovine retina were reconstit uted with recombinant phospholipase C-beta(2). Only isoprenylated beta (1) gamma(1) dimers were capable of stimulating phospholipase C-beta(2 ). The results show that gamma-subunit isoprenylation and/or additiona l post-translational processing of the protein are required for beta g amma subunit stimulation of phospholipase C.