Optical diffraction and image averaging of vertebrate muscle sections revealed that the myosin filament has 3-fold rotational symmetry, approximating a three-stranded helix.
The study demonstrates that vertebrate myosin filaments possess 3-fold rotational symmetry, suggesting the crossbridge array approximates a three-stranded helix.
Ultrathin transverse sections of the body muscle of bony fish and the sartorius muscle of frog have been analysed in detail by optical diffraction and image averaging to reveal the ultrastructures of the myosin filaments both in the M-region and in the outer ends of the filament (the tip region). The evidence is unequivocal that the myosin filaments in both muscle types have 3-fold rotational symmetry in all of the regions where symmetry can be seen. Using the nomenclature of Sjöström there can be little doubt that the symmetry of the crossbridge array approximates to that of a three-stranded helix (Squire, 1972). A model is proposed for the structure of the myosin filament in the vertebrate M-region. It explains the observed appearances without going into molecular detail. It is also suggested that it is the M-bridges at M4 that are primarily responsible for defining the two types of A-band structure (simple lattice and superlattice) and that the M1 bridges may have a secondary role.
Luther et al. (Thu,) conducted a other in Vertebrate muscle structure. Optical diffraction and image averaging was evaluated on Ultrastructure of myosin filaments. Optical diffraction and image averaging of vertebrate muscle sections revealed that the myosin filament has 3-fold rotational symmetry, approximating a three-stranded helix.