Genetic dissection of the final exocytosis steps in Paramecium tetraurelia cells: cytochemical determination of Ca2+-ATPase activity over preformed exocytosis sites

Abstract

In different Paramecium tetraurelia strains the occurrence of a Ca2+-ATPase (or p-nitro-phenylphosphatase) activity at the preformed attachment and exocytosis sites of the secretory vesicles (trichocysts) was analysed by electron-microscopic cytochemistry and X-ray microanalysis. In conjunction with freeze-fracture studies it was found that only those strains, which contain rosette particles, display this Ca2+-ATPase activity (7S, K 40I, nd 9 (18 degrees C), while other strains (nd 6, nd 9 (27 degrees C), tam 38) are devoid of both these characteristics. The presence (absence) of rosette particles and of Ca2+-ATPase activity at the preformed exocytosis sites is correlated with the capability (incapability) of performing exocytosis in these strains. We discuss several possible interpretations of this structure-function correlation.