Calmodulin and Calmodulin-regulated Protein Kinases as Transducers of Intracellular Calcium Signals

Abstract

Calcium serves as an intracellular signal transducer through its ability to reversibly interact with and modulate the structure and function of a class of proteins referred to as calcium-modulated proteins. One of these calcium-modulated proteins found in all eukaryotic cells is calmodulin (for review, see Van Eldik et al. 1982). Calmodulin is an integral subunit of a diverse array of enzymes and cytoskeletal structures and thus provides a common motif to one branch of the calcium signal transduction pathway. One class of enzymes that have calmodulin as the calcium-binding effector subunit are the protein kinases. It is through the proper expression and assembly of the calmodulin and protein kinase subunits that one set of signal transduction pathways are available to the eukaryotic cell. In this way, the chemical signal generated by a transient rise in the molar concentration of ionized intracellular calcium is transduced into a macromolecular conformational signal through...