Calmodulin (CaM) is a Ca2+-binding protein that is a key component of the Ca2+ second-messenger system and is involved in controlling many of the biochemical processes of cells.

Calmodulin is a small, acidic protein approximately 148 amino acids long (16706 Dalton) and, as such, is a favorite for testing protein simulation software. It contains four EF-hand "motifs" or domains, each of which binds a Ca2+ ion. It typically binds 0, 2, or 4 calcium ions, and binds and regulates different proteins in each state. There are over a hundred proteins known to bind calmodulin. It is highly conserved across all eukaryotes, and its expression is essential for biological cells to progress through mitosis.

Calmodulin-stimulated protein phosphatase (EC and calmodulin-dependent kinases are the major calmodulin-binding proteins in the brain.

Calmodulin 3D structure

Other calcium-binding proteins

Calmodulin belongs to one of the two main groups of calcium-binding proteins, called EF hand proteins. The other group, called annexins, bind calcium and phospholipid (e.g., lipocortin). Many other proteins bind calcium, although binding calcium may not be considered their principal function in the cell.


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