title: Calcium-induced conformational transition revealed by the solution structure of apo calmodulin.
abstract: The solution structure of Ca(2+)-free calmodulin has been determined by NMR spectroscopy, and is compared to the previously reported structure of the Ca(2+)-saturated form. The removal of Ca2+ causes the interhelical angles of four EF-hand motifs to increase by 36 degrees-44 degrees. This leads to major changes in surface properties, including the closure of the deep hydrophobic cavity essential for target protein recognition. Concerted movements of helices A and D with respect to B and C, and of helices E and H with respect to F and G are likely responsible for the cooperative Ca(2+)-binding property observed between two adjacent EF-hand sites in the amino- and carboxy-terminal domains.
authors.affiliation: Division of Molecular and Structural Biology, Ontario Cancer Institute, University of Toronto, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: T
authors.initials: T
authors.lastname: Tanaka
authors.forename: M
authors.initials: M
authors.lastname: Ikura
mesh_terms: D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism*; D003460:Crystallization; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008715:Methionine / Q000737:chemistry; D011487:Protein Conformation; D012996:Solutions
chemical_list: D002147:Calmodulin; D012996:Solutions; D008715:Methionine; D002118:Calcium