筋肉の細いフィラメントの構造とその変化

概要

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Low-angle X-ray diffraction patterns were recorded from crab leg muscles in living resting state and in rigor (glycerol-extracted). Both resting and rigor patterns showed a series of layer lines arising from helical arrangement of actin subunits in the thin filaments. In the resting state, the cross-over repeat of the long-pitch actin helices was 36.6nm, and the symmetry of the genetic actin helix was an intermediate between 26/12 and 28/13. When the muscle went into rigor, the cross-over repeat changed to 38.2nm and the helical symmetry to 28/13, with no detectable change in the axial repeat of actin subunits.<BR>In the rigor pattern, twelve other reflections were observed on the meridian and in the near-meridional region. These were indexed as orders of 2×38.3nm and could be assigned to troponin molecules; the meridional intensity peaks at even orders, the near-meridional intensity peaks at odd orders, and absence of the 12th, 14th and 16th orders could be explained by the model proposed by Ohtsuki (1974) for the arrangement of troponin molecules in the thin filaments. The pattern obtained from resting muscle showed several reflections assignable to troponin molecules; the positions of these reflections could also be explained by the Ohtsukis model.
日本生物物理学会の論文