title: Divalent cation-dependent ATPase activities in ciliary membranes and other surface structures in Paramecium tetraurelia: comparative in vitro studies.
abstract: Cilia membrane preparations from axenically grown Paramecium contain ATPase activities with distinct electrophoretic mobilities on Triton-polyacrylamide gels [M.J. Doughty and E.S. Kaneshiro (1983) J. Protozool. 30, 569-575]. Such gel analyses also show additional ATPase activity bands associated with ciliary axonemes (dyneins), cell pellicles, exocytotic trichocysts, and the external cell surface (ectoenzyme). In the present report, the in vitro properties of these activities in various cell fractions were compared. The activity in ciliary membranes was stimulated by Ca2+ greater than Mg2+, in pellicles by Ca2+ greater than Mg2+, and in trichocysts by Ca2+ = Mg2+. The ecto-ATPase was strictly Ca2+ dependent. Determination of the affinities for various phosphate-containing substrates showed that the activities in all fractions were nucleoside triphosphate phosphohydrolases. Unlike the axonemal dynein ATPases, all other fractions were vanadate- and p-chloromercuribenzoate-insensitive. Activities in all cell fractions were sensitive to ruthenium red, the ciliary membrane being the most sensitive (Ki = 4 microM). The ciliary membrane Ca2+ ATPase activity exhibited an apparent affinity for CaATP2- of 9 microM and was inhibited by other divalent cations, La3+, and phosphate, but not by ADP or AMP. The kinetic properties of the ciliary membrane Ca2+ ATPase activity in wild type and several behavioral mutants were similar except for those in the pawn mutant, d495, and the paranoiac mutant, d490, both of which had lower specific activities. These studies support the finding that the ciliary membrane ATPase activity of Paramecium is a specific Ca2+-dependent ATPase distinct from other divalent cation-dependent ATPase activities found in either the cilia or other cell surface structures.
authors.forename: M J
authors.initials: MJ
authors.lastname: Doughty
authors.forename: E S
authors.initials: ES
authors.lastname: Kaneshiro
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002413:Cations, Divalent; D002923:Cilia / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D009154:Mutation; D010247:Paramecium / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D002413:Cations, Divalent; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases