| Budget Amount *help |
¥6,800,000 (Direct Cost: ¥6,800,000)
Fiscal Year 1987: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1986: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1985: ¥5,500,000 (Direct Cost: ¥5,500,000)
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| Research Abstract |
The contraction of muscle is controlled by the Ca^<++>ion concentration in the cell.The protein,that plays an important role in the initial stage of muscle contraction,is troponin C (MW-18,000).The present project is concerned with the structural changes induce by the binding of Ca^<++>ions to troponin C in solution,studied by solution X-ray scattering technique. The results are summarized below.
1.The solution X-ray scattering from troponin C gives a distinct scattering profile in the moderate-angle region,in addition to the small-angle scattering.The profile changes as the binding of Ca^<++>ions to troponin C is controlled.
2.The small-angle scattering from troponin C solution consists of two "Guinier regions"(in a plot of ln[I(S)]vs.S^2).This behavior is throughly described by a Dumbbell-shaped molecule model.The analysis of the scattering profile by a dumbbell-shaped model affords three important structural parameters;The radius of gyration of of troponin C molecule, Rg(molecule),radius of gyration of N-and C-terminal domain of molecule,Rg(domain)and the distance between the centers of domains,r_<n-c>.
3.The Ca^<++>-free troponin C is described by the structural parameters,
Rg(molecule)=27.8A,
Rg(domain)=15.5A,
r_<n-c>=46.3A.
When the troponin C molecules bind with two/four Ca^<++>ions,the N-/C-terminal domain becomes more conpact,i.e.,Rg(domain)decrease from 15.5A-14.8A-14.6A. At the same time,the distance between the domains changes as 46.3A-37.3A-34.5A. This change is,in other words,the change of molecule itself,i.e.,the troponin C molecule becomes more compact as a whole.
These results are in accord with the structure of troponin C molecule that carries two Ca^<++>ions in crystal.
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