<p>Calmodulin (CaM) is a ubiquitous, calcium-binding protein that participates in numerous cellular regulatory processes. CaM mediates processes such as inflammation, metabolism, apoptosis, muscle contraction, intracellular movement, short-term and long-term memory, nerve growth and the immune response. CaM is expressed in many cell types and can have different subcellular locations, including the cytoplasm, within organelles, or associated with the plasma or organelle membranes. Many of the proteins that CaM binds are unable to bind calcium themselves, and as such use CaM as a calcium sensor and signal transducer.</p> <p>X-ray crystal structure of CaM reveals that the protein has a dumbell-shaped or EF-hand type structure consisting of two globular domains connected by seven-turn alpha-helix. The protein has four high affinity Ca2+-binding sites, two on each of its globular domains. CaM undergoes a conformational change upon binding to calcium, which enables it to bind to specific proteins for a specific response. Many calcium-binding proteins contain an EF-hand type calcium-binding domain [<cite idref="PUB00014021"/>, <cite idref="PUB00014022"/>]. These include: calbindin D9K, S100 proteins such as calcyclin, polcalcin phl p 7 (a calcium-binding pollen allergen), osteonectin, parvalbumin, calmodulin [<cite idref="PUB00014032"/>] family of proteins (troponin C, caltractin, cdc4p, myosin essential chain, calcineurin, recoverin, neurocalcin), plasmodial-specific Ca-binding protein Cbp40, penta-EF-Hand proteins [<cite idref="PUB00014023"/>] (sorcin, grancalcin, calpain), as well as multidomain proteins such as phosphoinositide-specific phospholipase C, dystrophin, Cb1 and alpha-actinin.</p><p>This entry represents a calcium-binding protein subfamily, with strong sequence similarity to CaM, which is an important component of Ca(2+)-mediated cellular signal transduction in the central nervous system, and which may augment or substitute for CaM [<cite idref="PUB00035530"/>].</p> Calcium binding protein