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 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 3.1.3.16) is the major calmodulin-binding protein in the brain.
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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