Calcium receptor protein calmodulin isolated from cilia and cells of Paramecium tetraurelia.

A low molecular weight protein of about 17 000 as determined by SDS-polyacrylamide gel electrophoresis has been isolated from cilia and cell bodies, respectively, from Paramecium tetraurelia (wildtyp 51s). This protein has been identified as calmodulin by various properties previously ascribed to calmodulin from other vertebrate and invertebrate systems. These properties are heat stability, electrophoretic mobility and its ability to activate in the presence of calcium a calmodulin-dependent phosphodiesterase from pig brain. Calmodulin is present in rather high amounts in cell bodies (75 micrograms/g) and also in isolated cell-free cilia (up to 50 micrograms/g). Its presence in cilia suggests a role in the control of ciliary activity.