Presence and indirect immunofluorescent localization of calmodulin in Paramecium tetraurelia.

Abstract

The presence and localization of calmodulin, a Ca-dependent regulatory protein, is demonstrated in the ciliated protozoan P. tetraurelia. Calmodulin is demonstrated by several criteria: the ability of whole cell Paramecium extracts to stimulate mammalian phosphodiesterase activity, the presence of an acidic, thermostable, 17,000-dalton polypeptide whose mobility shifts in sodium dodecyl sulfate polyacrylamide gel electrophoresis in the presence of Ca2+ and the affinity of antibodies against mammalian calmodulin for a Paramecium component as demonstrated by indirect immunofluorescent localization and radioimmunoassay. Indirect immunofluorescence studies reveal that Paramecium calmodulin is distributed in 3 distinct regions of the cell, i.e., large, spherical cytoplasmic organelles representing perhaps the food vacuoles or other vacuolar inclusions of the cell, along the entire length of oral and somatic cilia and along a linear punctate pattern corresponding to the kinetics (basal bodies) of the cell.