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Eur J Cell Biol. 1996 Aug;70(4):339-46.

The major ciliary membrane proteins in Paramecium primaurelia are all glycosylphosphatidylinositol-anchored proteins.

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Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, associé à l'Université Pierre et Marie Curie, Gif-sur-Yvette, France.


Using a strategy based upon specific features of membrane proteins linked to the plasma membrane by a glycosylphosphatidylinositol (GPI) anchor, we have studied in the strain 513 of Paramecium primaurelia the glycosylphosphatidylinositol (GPI) proteins both in their membrane-bound and soluble forms. 35S-Labeling associated with bacterial phosphatidylinositol-specific phospholipase C treatment of purified cilia allowed the identification of soluble GPI proteins (devoid of their lipid moiety), released from cilia. By labeling with 88[33P]phosphoric acid and [3H]ethanolamine, respectively, we identified membrane-bound GPI proteins, when anchored in the cilia membrane via the lipid of their GPI tail. We demonstrated that, in addition to the SAg (surface antigen) which is a high molecular weight protein implicated in the antigenic variation phenomenon, three other ciliary membrane proteins were also GPI-anchored. The membrane-bound and soluble forms of these GPI proteins had apparent molecular weights, in unreduced conditions, of 30,000 and 40 to 50,000, respectively. We named these surface GPI proteins SGPs, SGP1 to SGP3, SGP1 (surface GPI protein 1) and SGP2 (surface GPI protein 2) were the most abundantly expressed. Only SGP2 displayed a rapid turnover. By phosphatidylinositol-specific phospholipase C treatment of the membrane proteins recovered in the detergent phase, following partitioning with Triton X-114, we demonstrated that the SAg and SGPs are the major ciliary membrane proteins of P.primaurelia.

[Indexed for MEDLINE]

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