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.
Highlights
Dependent shape change of pig brain calmodulin in detail
We propose that the shape of calmodulin differs greatly from that of a dumbbell structure with the increasingof calcium binding in the pres
A of Bragg spacing (s = l/d, d, Bragg spacing), the hump would be a characteristic profile of a dumbbell structure in which the N-lobe correlates with the C-lobe at a distance of
Summary
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. Using the SR radiation as an x-ray source, we could obtain the scattering profiles of calmodulin in high quality at a moderate angle regionwhich enables us to give direct information about domain topologies.
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