Regulation of phosphoinositide and phosphatidylcholine phospholipases by G proteins.
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.
Exton
J H
JH
Howard Hughes Medical Institute, Department of Molecular Physiology and Biophysics, Nashville, TN.
Taylor
S J
SJ
Blank
J S
JS
Bocckino
S B
SB
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*
D010727:Phosphoric Diester Hydrolases; D010738:Type C Phospholipases; D010739:Phospholipase D; D019204:GTP-Binding Proteins; D043265:Phosphatidylinositol Diacylglycerol-Lyase