Subcellular distribution of calmodulin and calmodulin-binding sites in Tetrahymena pyriformis

The subcellular distribution of calmodulin and particulate calmodulin-binding activity was studied in a eukaryotic protozoan, Tetrahymena pyriformis NT-1. The particulate calmodulin-binding activity was found to be localized principally in microsomes and to some extent in cilia and surface membranes called pellicles. Nearly all (93%) of the total amount of calmodulin was recovered in two soluble compartments, the ciliary and postmicrosomal supernatant fractions.