Binding of both Ca2+ and mastoparan to calmodulin induces a large change in the tertiary structure.
The technique of small-angle X-ray scattering has been employed to examine the solution conformation of calmodulin and its complexes with Ca2+ alone, and with both Ca2+ and mastoparan. The radius of gyration decreased by 3.1 +/- 0.3 A upon binding of both 4 mol Ca2+/mol of protein and 1 mol mastoparan/mol of protein to form the ternary complex. A smaller increase was found for the separate binding of 4 mol Ca2+/mol of protein in the absence of mastoparan (0.6 +/- 0.3 A). The analyses of pair distance distribution function showed that the maximal pair distance in calmodulin complex with both Ca2+ and mastoparan decreased by 20-30% in comparison with calmodulin or its complex with Ca2+, and a shoulder near 40 A, which characterizes the dumbbell-shaped molecule of calmodulin, disappeared. These results indicate that the two globular domains of the calmodulin complex with Ca2+ and mastoparan come close together by 8.0-9.5 A on average, if the size and the overall shape of the globular domains are the same in Ca2+-calmodulin-mastoparan complex as in calmodulin or Ca2+-calmodulin complex.
Matsushima
N
N
School of Allied Health Professions, Sapporo Medical College, Hokkaido.
Izumi
Y
Y
Matsuo
T
T
Yoshino
H
H
Ueki
T
T
Miyake
Y
Y
D000818:Animals; D001514:Bee Venoms / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D036341:Intercellular Signaling Peptides and Proteins; D008027:Light; D010455:Peptides; D011485:Protein Binding; D011487:Protein Conformation; D012542:Scattering, Radiation; D013552:Swine; D013696:Temperature; D014862:Wasp Venoms / Q000378:metabolism*
D001514:Bee Venoms; D002147:Calmodulin; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D014862:Wasp Venoms; C037500:mastoparan; D002118:Calcium