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.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Biological Chemistry|
|State||Published - 1992|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology