Sandbox 213: Difference between revisions

Up to four calcium ions are bound by calmodulin via its four EF hand motifs. EF hands supply an electronegative environment for ion coordination. After calcium binding, hydrophobic methyl groups from methionine residues become exposed on the protein via conformational change.  

This presents hydrophobic surfaces, which can in turn bind to Basic Amphiphilic Helices (BAA helices) on the target protein. These helices contain complementary hydrophobic regions. The flexibility of Calmodulin's hinged region allows the molecule to "wrap around" its target. This property allows it to tightly bind to a wide range of different target proteins. <ref name="Houdusse A, Gaucher JF, Krementsova E, Mui S, Trybus KM, Cohen C. Crystal structure of apo-calmodulin bound to the first two IQ motifs of myosin V reveals essential recognition features. Proc Natl Acad Sci U S A. 2006 Dec 19;103(51):19326-31. Epub 2006 Dec 6. PMID :[[17151196]]"/>. </StructureSection>

This encourages the target sequence to adopt an α-helical arrangement so that it occupies the center of a hydrophobic tunnel.

The consequence of this interaction is a conformational change in the target, a state that persists only as long as the Ca²⁺ concentration remains high <ref name="Fallon JL, Quiocho FA. A closed compact structure of native Ca(2+)-calmodulin. Structure. 2003 Oct;11(10):1303-7. PMID :[[14527397]]"/>.