Calmodulin is a major component of extruded trichocysts from Paramecium tetraurelia.
Extruded trichocysts are composed of a family of proteins with molecular weights between 15,000 and 20,000. We have used heat treatment and affinity chromatography on fluphenazine-Sepharose to purify calmodulinlike proteins from whole cells and from extruded trichocysts. The purified protein from trichocysts is indistinguishable from that of whole cells; it is heat-stable, activates brain phosphodiesterase in a Ca++-dependent fashion, changes mobility on SDS polyacrylamide gels in the presence of Ca++, contains 1 mol of trimethyllysine/17 kdaltons, and has the amino acid composition characteristic of calmodulins. Calmodulin is a major component of purified, extruded trichocysts, of which it represents between 1 and 10% by mass. The other proteins of the trichocyst also resemble calmodulin in several properties. Possible roles for calmodulin in the Ca++-activated extrusion of trichocysts is discussed.
D000818:Animals; D002118:Calcium / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002147:Calmodulin / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D003594:Cytoplasmic Granules / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005089:Exocytosis; D010247:Paramecium / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D010727:Phosphoric Diester Hydrolases; D002118:Calcium