Calpain

spinqualitylabelsall models Human calpain1 large subunit complex with inhibitor and Ca+2 ions (green) (PDB entry 1zcm) Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Function Calpains (CAP) are calcium-dependent cysteine proteases. CAPs are regulated by Ca+2 concentration, phosphorylation and calpastatin. The CAP family contains 14 members. CAP1 (or mu-CAP) and CAP2 (or M-CAP) T are the best characterized CAPs. CAP2 limits the extent of neuronal plasticity and learning. CAP3 is expressed in skeletal muscles and regulates sarcomere remodelling. CAP7 is atypical CAP that lacks a penta-EF-hand domain. CAP8 and CAP9 are involved in the mucosal defense against stress-induced gastropathies. CAP9 has been identified as the tumor suppressor for gastric cancer. CAP13 is expressed in testis and lungs. Disease CAP3 defects lead to a certain muscular dystrophy. Defective CAPs have a role in neurodegeneration. Structural highlights CAP is a heterodimer containing a small 28kDa regulatory subunit which is identical for all CAPs and a large 80kDa catalytic subunit. CAP undergoes conformational change upon binding of Ca+2 ions resulting in closing of its active site cleft and activation as a cysteine protease. Inhibitor binding site. Water molecules are shown as red spheres. Covalent bond between Cys 115 of human calpain1 large subunit with inhibitor. 1st Ca+2 coordination site. 2nd Ca+2 coordination site. 3D structures of calpain Calpain 3D structures

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