title: Regulation of phosphoinositide and phosphatidylcholine phospholipases by G proteins.
abstract: Two G proteins that regulate phosphoinositide phospholipase C in liver plasma membranes have been purified to homogeneity in both the heterotrimeric and dissociated forms. The heterotrimers contain a 42 kDa or 43 kDa alpha subunit and a 35 kDa beta subunit. The alpha subunits are not ADP-ribosylated by pertussis toxin and are closely related immunologically to members of the recently identified Gq class of G proteins. The specific phosphoinositide phospholipase C isozyme that responds to the G proteins has been determined to the beta 1 isozyme. GTP analogues stimulate phosphatidylcholine hydrolysis in rat liver plasma membranes. The nucleotide specificity and Mg2+ dependency of the response indicate that it is mediated by a G protein. Phosphatidic acid, diacylglycerol, choline and phosphorylcholine are the products, indicating that both phospholipase D and C activities are involved. Activation of phospholipase D is also indicated by the enhanced production of phosphatidyl-ethanol in the presence of ethanol.
authors.affiliation: Howard Hughes Medical Institute, Department of Molecular Physiology and Biophysics, Nashville, TN.
authors.forename: J H
authors.initials: JH
authors.lastname: Exton
authors.forename: S J
authors.initials: SJ
authors.lastname: Taylor
authors.forename: J S
authors.initials: JS
authors.lastname: Blank
authors.forename: S B
authors.initials: SB
authors.lastname: Bocckino
mesh_terms: D000818:Animals; D019204:GTP-Binding Proteins / Q000502:physiology*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010739:Phospholipase D / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism*
chemical_list: D010727:Phosphoric Diester Hydrolases; D010738:Type C Phospholipases; D010739:Phospholipase D; D019204:GTP-Binding Proteins; D043265:Phosphatidylinositol Diacylglycerol-Lyase