Structural changes of the regulatory proteins bound to the thin filaments in skeletal muscle contraction by X-ray fiber diffraction
- Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan)
- Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)
- School of Nursing, Teikyo Heisei Junior College, Ichihara, Chiba 290-0158 (Japan)
In order to clarify the structural changes related to the regulation mechanism in skeletal muscle contraction, the intensity changes of thin filament-based reflections were investigated by X-ray fiber diffraction. The time course and extent of intensity changes of the first to third order troponin (TN)-associated meridional reflections with a basic repeat of 38.4 nm were different for each of these reflections. The intensity of the first and second thin filament layer lines changed in a reciprocal manner both during initial activation and during the force generation process. The axial spacings of the TN-meridional reflections decreased by {approx}0.1% upon activation relative to the relaxing state and increased by {approx}0.24% in the force generation state, in line with that of the 2.7-nm reflection. Ca{sup 2+}-binding to TN triggered the shortening and a change in the helical symmetry of the thin filaments. Modeling of the structural changes using the intensities of the thin filament-based reflections suggested that the conformation of the globular core domain of TN altered upon activation, undergoing additional conformational changes at the tension plateau. The tail domain of TN moved together with tropomyosin during contraction. The results indicate that the structural changes of regulatory proteins bound to the actin filaments occur in two steps, the first in response to the Ca{sup 2+}-binding and the second induced by actomyosin interaction.
- OSTI ID:
- 21143635
- Journal Information:
- Biochemical and Biophysical Research Communications, Vol. 369, Issue 1; Other Information: DOI: 10.1016/j.bbrc.2007.11.088; PII: S0006-291X(07)02489-8; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0006-291X
- Country of Publication:
- United States
- Language:
- English
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