Calmodulin (CAM)

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Calmodulin (CAM) is inferred to be encoded in all eukaryotes and expressed in most cells. In its four calcium form it activates over twenty target enzymes or structural proteins [6]. Pairs of domains 1&2 are connected to lobe 3-4 by an eight residues linker. Helix F2, the linker, and helix E3 form a seven turn _-helix. The linker serves as a flexible tether. In the apo-form both lobes are in the closed conformation and the tether is extended; CAM is then dumbbell shaped. In the Ca4-form the tether is bent, both lobes are in an open conformation, and the two lobes enfold a helix of the target protein [7]. The ten subfamilies (CAM, TNC, ELC, RLC TPNV, CLAT, SQUD, CDC, CAL, and CAST) are congruent (figure 5).