title: Phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis as a probe for the distribution of phosphatidylinositol in hepatocyte membranes.
abstract: Phosphatidylinositol-specific phospholipase C (PI-PLC) produced by Bacillus thuringiensis has been used as a probe for the distribution of phosphatidylinositol in hepatocyte membranes. Approx. 50% of this phospholipid was hydrolysed in microsomal vesicles (endoplasmic reticulum) with no significant hydrolysis of the remaining membrane phospholipids. Latency of mannose-6-phosphatase was retained during treatment indicating that the vesicles remained impermeable. Stripping of the ribosomes did not increase hydrolysis of phosphatidylinositol; however, when the vesicles were opened using dilute sodium carbonate, hydrolysis increased to greater than 90%. Hydrolysis of phosphatidylinositol of Golgi membranes was 35% and of plasma membranes was 50%. After treatment with PI-PLC, radiolabelled secretory proteins were retained in Golgi membranes and trapped lactate dehydrogenase was retained in plasma-membrane preparations indicating that the vesicles remained closed. Hydrolysis of phosphatidylinositol increased to greater than 90% when the membranes were opened by treatment with dilute sodium carbonate. These observations indicate that PI-PLC of Bacillus thuringiensis is a suitable probe for the distribution of phosphatidylinositol in membranes, and that in liver membranes this phospholipid occurs on each side of the bilayer, a topography consistent with its diverse roles.
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, U.K.
authors.forename: J A
authors.initials: JA
authors.lastname: Higgins
authors.forename: B W
authors.initials: BW
authors.lastname: Hitchin
authors.forename: M G
authors.initials: MG
authors.lastname: Low
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000201:enzymology*; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D006868:Hydrolysis; D008099:Liver / Q000378:metabolism / Q000648:ultrastructure*; D008862:Microsomes, Liver / Q000378:metabolism; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000378:metabolism*; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D051381:Rats
chemical_list: D010716:Phosphatidylinositols; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase