Three-dimensional reconstruction from tilted sections of fish muscle M-band

Abstract

Fish muscle provides a particularly suitable specimen for studying the organization of thick filaments in vertebrate striated muscle because the filaments are arranged with a single orientation on a well ordered hexagonal lattice¹. The M-band consists of sets of cross-links, which join the myosin filaments in the middle of the A-band. Previous work¹ concluded that the fish muscle M-band had the local symmetry of the dihedral point group 32. We present here a quantitative analysis of transverse sections of the M-band, using general methods² developed for crystalline layers, to combine various tilted views. The three-dimensional map computed to a resolution of about 70 Å confirms previous findings¹; it shows new features of the thick filament structure in the M-band region and provides new information on the use of three-dimensional reconstruction from sectioned biological material. The accompanying paper³ describes a novel technique of three-dimensional reconstruction of the fish M-band from a single view of a slightly oblique plastic section.