CHOPA10.14 and Molt4–1D10 are defective in inositol acylation of a synthetic substrate GlcN-PI(C8). The membranes of wild-type CHO (lanes 1 and 3) and CHOPA10.14 (lanes 2) cells were incubated with [3H]palmitoyl-CoA in the presence (lanes 1 and 2) or absence (lane 3) of GlcN-PI(C8). The membranes of wild-type Molt4 (lane 4), Molt4–1D10 transfected with PIG-W (lanes 5 and 6), and 1D10 mutant (lane 7) were incubated with [3H]palmitoyl-CoA in the presence (lanes 4, 5, and 7) or absence (lane 6) of GlcN-PI(C8). After 10-min-incubation, lipids were analyzed by TLC with a solvent system of chloroform/methanol/0.25% KCl (55:45:10). *, GlcN-acylPI(C8); **, GlcN-PI(C8)-dependent extraspot of unknown structure.