Calcium-free Calmodulin: Difference between revisions

{{STRUCTURE_1cfc|  PDB=1cfc  |  SCENE=Sandbox_190/1cfc/1  }}

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> It consists of 148 residues and is somewhat shaped like a dumbell, where one end is an N-terminal domain, the other end is the C-terminal domain, and they are connected by a link of about 5 residues. <ref name="4CRT"/> It is also part of the "EF hand" superfamily, named after the pair of helix-loop-helix motifs present in its N and C domains. <ref name="4CRT"/> 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>  

=='''Calcium-bound Calmodulin'''==

[[Image:3cln.png|left|200px]]

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, but to no avail, thus it was decided that the only way to get a good idea of the structure would be to use several NMR experiments. <ref name="4CRT"/>