Calmodulin-dependent calcium signal transduction.

Calmodulin (CaM) is a ubiquitous, intracellular calcium-receptive protein. Biopharmacological studies using CaM antagonists suggest that CaM is involved in mechanisms of stimulus-induced cellular responses such as smooth muscle contraction, secretion of nonmuscle cells and cell proliferation. Results with these CaM antagonists, hydrophobic fluorescent probes, hydrophobic chromatography, and alternative activators of Ca2+, CaM-dependent enzyme revealed that calcium ion induces conformational changes in CaM that expose hydrophobic regions on the surface of the molecule, and these regions may act as sites of interaction with its target enzymes and CaM antagonists. Moreover, a similar molecular mechanism of calcium signal transduction was also observed with other calcium-modulated proteins such as troponin C and S100 protein.