Identification in bovine liver plasma membranes of a Gq-activatable phosphoinositide phospholipase C.
Phosphoinositide phospholipase C (PLC) activity extracted from bovine liver plasma membranes with sodium cholate was stimulated by GTP gamma S-activated G alpha q/G alpha 11, whereas the enzyme from liver cytosol was not. The membrane-associated PLC was subjected to chromatography on heparin-Sepharose, Q Sepharose, and S300HR, enabling the isolation of the G-protein stimulated activity and its resolution from PLC-gamma and PLC-delta. Following gel filtration, two proteins of 150 and 140 kDa were found to correspond to the activatable enzyme. These proteins were identified immunologically as members of the PLC-beta family and were completely resolved by chromatography on TSK Phenyl 5PW. The 150-kDa enzyme was markedly responsive to GTP gamma S-activated alpha-subunits of G alpha q/G alpha 11 or to purified Gq/G11 in the presence of GTP gamma S. The response of this PLC was of much greater magnitude than that of the 140-kDa enzyme. The partially purified 150-kDa enzyme showed specificity for PtdIns(4,5)P2 and PtdIns4P as compared to PtdIns and had an absolute dependence upon Ca2+. These characteristics were similar to those of the brain PLC-beta 1. The immunological and biochemical properties of the 150-kDa membrane-associated enzyme are consistent with its being the PLC-beta isozyme that is involved in receptor-G-protein-mediated generation of inositol 1,4,5-triphosphate in liver.
Shaw
K
K
Howard Hughes Medical Institute, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
Exton
J H
JH
D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010727:Phosphoric Diester Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D015398:Signal Transduction
D007527:Isoenzymes; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D010727:Phosphoric Diester Hydrolases; D019204:GTP-Binding Proteins; D043265:Phosphatidylinositol Diacylglycerol-Lyase