Calmodulin: an overview.

Calmodulin is a 16,700-dalton Ca2+-binding protein ubiquitous in the eukaryotes. It has no intrinsic enzymatic activity, but it regulates a wide spectrum of enzymes that control many basic cellular processes, ranging from the metabolism of cyclic nucleotides, Ca2+, and glycogen to contractile activity and stimulus-secretion coupling. Mounting evidence now indicates that calmodulin is the major intracellular Ca2+ receptor that remained elusive despite three decades of extensive work by many investigators.