glycosyl-phosphatidylinositol-anchored protein assembly

The role of glycosyl-Ptdlns (GPI)-anchored proteins in the cytodifferentiation of Tetrahymena vorax was examined. Labelling of cells with [3H]myristate or [3H]palmitate followed by electrophoresis showed an array of proteins carrying covalently bound lipids. El6ctrophoresis of protein from cells labelled with the GPI-anchor components [3H]Ins and [14C]ethanolamine revealed three polypeptides on fluorograms which have apparent molecular masses of approx. 28, 50 and 82 kDa. Labelled lipid associated with these polypeptides was susceptible to release by in vitro exposure to Bacillus thuringiensis Ptdlns-specific phospholipase C (PI-PLC). Using labelled fatty acids, cells induced to differentiate showed altered GPI-anchored protein-labelling patterns in comparison with undifferentiated control cells, with a heavily labelled 32 kDa band appearing upon differentiation.