Possible involvement of a calmodulin regulated Ca2+ -ATPase in exocytosis performance in Paramecium tetraurelia cells.
Surface membrane fractions from Paramecium tetraurelia cells contain a calmodulin-stimulated Ca2+-ATPase responding to low levels of free Ca2+ and with features characteristic of a membrane-bound ATPase. Among the different strains analyzed this enzyme was practically absent selectively from the 'non-discharge' mutant nd9-28 degrees C (from J. Beisson): if cultured at a permissive temperature (18 degrees C), this strain showed identical values of calmodulin-stimulated Ca2+-ATPase activity as wild-type cells (7S) or strains with mutations which do not affect exocytosis performance. We conclude that this calmodulin-stimulated Ca2+-activated ATPase might be a prerequisite for membrane fusion in the course of exocytosis performance.
D000818:Animals; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000302:isolation & purification / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology; D005089:Exocytosis / Q000187:drug effects*; D007700:Kinetics; D008970:Molecular Weight; D010247:Paramecium / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D000252:Calcium-Transporting ATPases