Calmodulin: an introduction.

Calmodulin is the most widely distributed and most versatile member of a family of calcium-binding proteins which probably serve as receptors for the Ca2+ signal. Through the regulation of a wide variety of intracellular enzymes, calmodulin plays a key role in many physiological processes. An understanding of the different mechanisms by which calmodulin exerts its influence is beginning to emerge and an interesting hypothesis regarding the interrelationship between the cAMP and Ca2+ second messenger systems has recently been put forward.