Calcium-free Calmodulin: Difference between revisions

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==='''General Information'''===
==='''General Information'''===
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Calmodulin is a molecule that has been studied extensively in its functions within the cell, and has an important role in relaying Ca2+ signals within the cytosol. <ref name="1CRT">Hoeflich, K.P., & Ikura, M.. Calmodulin in action: diversity in target recognition and activation mechanisms, Cell. 2002 108:739-742</ref> It does this by binding to Ca2+, undergoing a conformational change, and may interact with various proteins within the cell.<ref name=”5CRT”/><ref name="4CRT">Kuboniwa H, Tjandra N, Grzesiek S, Ren H, Klee CB, Bax A. Solution structure of calcium-free calmodulin. Nat Struct Biol. 1995 Sep;2(9):768-76. PMID:7552748</ref><ref name="3CRT">Babu YS, Bugg CE, Cook WJ. Structure of calmodulin refined at 2.2 A resolution. J Mol Biol. 1988 Nov 5;204(1):191-204. PMID:3145979</ref> Once bound to a target protein, it undergoes a further conformational change and may activate certain systems. For example, there is a Ca2+ pump in the plasma membrane pump that is activated by the binding of Ca2+-bound calmodulin, and then uses ATP to drive the Ca2+ out of the cell. <ref name="6CRT">Berridge MJ, Bootman MD, Roderick HJ. Calcium signalling: dynamics, homeostasis and remodelling. Nature Reviews. Molecular Cell Biology, 2003 4(7), pp. 517-29; PMID: 12838335</ref>  
Calmodulin is a molecule that has been studied extensively in its functions within the cell, and has an important role in relaying Ca2+ signals within the cytosol. <ref name="1CRT">Hoeflich, K.P., & Ikura, M.. Calmodulin in action: diversity in target recognition and activation mechanisms, Cell. 2002 108:739-742</ref> It does this by binding to Ca2+, undergoing a conformational change, and may interact with various proteins within the cell.<ref name="1CRT"/><ref name="4CRT">PMID: 7552748</ref><ref name="3CRT">PMID: 3145979</ref> Once bound to a target protein, it undergoes a further conformational change and may activate certain systems. For example, there is a Ca2+ pump in the plasma membrane pump that is activated by the binding of Ca2+-bound calmodulin, and then uses ATP to drive the Ca2+ out of the cell. <ref name="6CRT">PMID: 12838335</ref>  


[[Image:3cln.png|left|200px]]
[[Image:3cln.png|left|200px]]
==='''Calcium-bound Calmodulin'''===
==='''Calcium-bound Calmodulin'''===
The structure of calcium-bound calmodulin had previously been discovered using x-ray crystallography <ref name=”1CRT”/>. Later attempts were  
The structure of calcium-bound calmodulin had previously been discovered using x-ray crystallography <ref name="3CRT"/>. It was then theorized that knowledge of the structure of calcium-free calmodulin would give greater insight into the function of the protein. Attempts were made to crystallize the calcium-free (or apo) form,