| Project/Area Number |
06452443
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Biophysics
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| Research Institution | Osaka University |
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Principal Investigator |
WAKABAYASHI Katsuzo FACULTY OF ENGINEERING SCIENCE,BIOPHYSICAL ENGINEERING,ASSOCIATE PROFESSOR, 基礎工学部, 助教授 (00029521)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥5,200,000 (Direct Cost: ¥5,200,000)
Fiscal Year 1995: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1994: ¥4,000,000 (Direct Cost: ¥4,000,000)
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| Keywords | X-Ray Diffraction / Structural Analyzes / Muscle Contraciton / Thin Filament Structure / Myosin Head / Actomyosin Complex / Synchrotron Radiation / Imaging Plate / X線回折 |
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| Research Abstract |
[1] Structural change of the thin filaments during contraction of frog skeletal muscle
Firstly, we measured precisely the spacing changes of the actin filament-based reflections in the X-ray diffraction pattern from an isometrically contracting muscle using synchrotron radiation. We found 0.2-0.3% of extnsion in the actin filaments as well as the myosin filaments. Such filament extensibility was elastic. These results provided a great insight to a force-generation mechanism in muscle. Secondly, we measured intensities of the thin filament-based layr lines up to -13A.Using the atomic data of the actin monomer and tropomyosin, we constructed a model of the thin filament and calculated a difference Fourier, indicating that the structural change occurred within the thin filaments. Modeling studies revealed distinct changes of the domain structure of actin in the filament which were induced by interaction with myosin heads. Tropomyosin molecules also moved in the azimuthal direction by about
… More
5A,less than previously postulated in a steric block hypothesis of muscle regulation.
[2] Conformational changes of the myosin head and the solution structure of an actomyosin complex
Synchrotron X-ray solution scattering revealed that the myosin head altered its conformation during an hydrolysis of ATP : the radius of gyration and maximum chord length decreased by 3A and 10A,respectively. Modeling studies using the atomic data indicated that the light chain-binding domain rotated around the amino acid 711 by 12ﾟ downward by 10ﾟ in the plane including its long axis. From the experiments with nucleotide analogs, the conformational changes occurred in the ADP.P_i state and reversed in the product release steps. We succeeded in preparing non-polymerized actin-myosin head complex and investigated the solution structure of this complex by X-ray solution scattering. The result indicated that the actin monomer bound to the proximal end of the catalytic domain of the myosin head with a center-to-center distance of 75A.Such studies have opened a very important root to structural studies of the smallest energy transducing unit in the actomyosin system. Less
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