title: Calcium-induced shape change of calmodulin with mastoparan studied by solution X-ray scattering.
abstract: Solution x-ray scattering using synchrotron radiation as an x-ray source was used to analyze the Ca2+-dependent shape change of pig brain calmodulin in detail. The radius of gyration of calmodulin at 10 mg/ml was increased by 0.9 A. The increase was nearly completed when 2.5 mol of Ca2+/mol of calmodulin was added, whereas the radius of gyration of calmodulin with mastoparan decreased by about 3 A with an increasing Ca2+ concentration up to 4 mol of Ca2+/mol of calmodulin. At a moderate angle of region, both scattering profiles from calmodulin with or without Ca2+ displayed clear humps at s = 0.03 A-1 which are characteristic of a dumbbell structure. However, in the presence of mastoparan, the hump in the scattering profile became obscure and later disappeared with the third and fourth Ca2+ binding to calmodulin. These findings are attributable to the Ca2+-induced shape change of calmodulin with mastoparan from a dumbbell structure to a non-dumbbell structure in which the distance between the two lobes of calmodulin become closer by a bend in the central helix.
authors.affiliation: Department of Chemistry, Sapporo Medical College, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yoshino
authors.forename: O
authors.initials: O
authors.lastname: Minari
authors.forename: N
authors.initials: N
authors.lastname: Matsushima
authors.forename: T
authors.initials: T
authors.lastname: Ueki
authors.forename: Y
authors.initials: Y
authors.lastname: Miyake
authors.forename: T
authors.initials: T
authors.lastname: Matsuo
authors.forename: Y
authors.initials: Y
authors.lastname: Izumi
mesh_terms: D000818:Animals; D001514:Bee Venoms / Q000378:metabolism*; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000302:isolation & purification / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D011487:Protein Conformation / Q000187:drug effects; D013552:Swine; D014862:Wasp Venoms / Q000378:metabolism*; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D001514:Bee Venoms; D002147:Calmodulin; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D014862:Wasp Venoms; C037500:mastoparan; D002118:Calcium