title: Inositol acylation of a potential glycosyl phosphoinositol anchor precursor from yeast requires acyl coenzyme A.
abstract: Glycosyl phosphoinositol (GPI) anchors on proteins can be modified by palmitoylation of their inositol residue, which makes such anchors resistant to cleavage by phosphatidylinositol-specific phospholipase C (PI-PLC) (Roberts, W. L., Myher, J. J., Kuksis, A., Low, M. G., and Rosenberry, T.L. (1988) J. Biol. Chem. 263, 18766-18775). Mannosylated GPI lipids made in trypanosomal and mammalian cells can also be inositol-acylated, indicating that inositol acylation may be a normal step in GPI anchor synthesis. We find that Saccharomyces cerevisiae mutants blocked in dolichyl phosphate mannose synthesis accumulate a lipid that can be radiolabeled in vivo with [3H]myo-inositol, [3H]GlcN, and [3H]palmitic acid. This lipid is resistant to PI-PLC, yet sensitive to mild alkaline hydrolysis, and has been characterized as GlcN-phosphatidylinositol (PI), fatty acylated on its inositol residue. When yeast membranes are incubated with UDP-[14C] GlcNAc, 14C-labeled GlcNAc-PI and GlcN-PI are made. Addition of ATP and CoA, or of palmitoyl-CoA to incubations results in the synthesis of [14C]GlcN-(acyl-inositol)PI. This lipid is also made when membranes are incubated with [1-14C]palmitoyl-CoA and UDP-GlcNAc. We propose that acyl CoA is the donor in inositol acylation of GlcN-PI, and that GlcN-(acyl-inositol)PI is an obligatory intermediate in GPI synthesis.
authors.affiliation: Department of Biochemistry, University of Illinois, Urbana 61801.
authors.forename: L C
authors.initials: LC
authors.lastname: Costello
authors.forename: P
authors.initials: P
authors.lastname: Orlean
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism*; D000215:Acylation; D002855:Chromatography, Thin Layer; D006017:Glycolipids / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols; D007294:Inositol / Q000378:metabolism*; D050356:Lipid Metabolism; D010171:Palmitoyl Coenzyme A / Q000378:metabolism; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000378:metabolism*; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D000214:Acyl Coenzyme A; D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D010716:Phosphatidylinositols; D010171:Palmitoyl Coenzyme A; D007294:Inositol; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase