J. Biol. Chem., Vol. 266, Issue 23, 15048-15053, 08, 1991
Phosphatidylinositol-linked glycans and phosphatidylinositol-anchored proteins of Tetrahymena mimbres
PE Ryals, Y Pak and GA Thompson Jr
Department of Botany, University of Texas, Austin 78713.
The insoluble residue from Tetrahymena mimbres cells that had been
preincubated in vivo for 2 h with [3H]myristic acid and then exhaustively
delipidated with organic solvents retained radioactivity, principally in
material which migrated on sodium dodecyl sulfate- polyacrylamide gel
electrophoresis with an apparent molecular mass of 10-14 kDa. This material
was extractable from the delipidated cell residue with organic solvents
known to solubilize phosphatidylinositol glycans (PI glycans). The same
material could also be labeled with [3H]inositol, [14C]glucosamine, and
[3H] ethanolamine. When the delipidated residue of cells labeled for 2 h
with [3H]myristate was treated with phosphatidylinositol-specific
phospholipase C or nitrous acid, much of the associated radioactivity was
released. A similar release was obtained using the putative PI glycan
fraction extracted from the cell residue. After further purification by
thin layer chromatography, this latter material was hydrolyzed with HCl and
shown to contain fatty acids, alkylglyceryl ethers, phosphate, inositol,
glucosamine, mannose, and ethanolamine. The findings indicate that T.
mimbres contains PI glycans resembling in structure those recently
characterized in trypanosomes and mammalian cells. As the time of
incubation with the radiotracers enumerated above was increased to 6-24 h,
increasing amounts of radioactivity appeared in the 22-27-kDa region of
sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels. This higher
molecular weight material is shown in the companion paper (Pak, Y., Ryals,
P.E., and Thompson, G.A., Jr. (1991) J. Biol. Chem. 266, 15054-15059) to be
released by in vivo phosphatidylinositol-specific phospholipase C
treatment. Thus T. mimbres contains a pool of free PI glycans and at least
one phosphatidylinositol-anchored protein.