Studies on the Helical Segment of the Myosin Molecule

Some sort of cyclic interaction of the globular units, the “heads” of the myosin molecule, with ATP and with actin of the thin filaments is accepted by most of the authors to be the primary force-generating event in muscle activity. This explains the wide interest devoted to HMM and HMM-S-1, the fragments containing the “heads.” The functional role of the long, helical “tail” of the myosin molecule, however, can not be regarded as secondary. Aggregation of the myosin molecules to form the thick filaments secures the exact geometry of the heads relative to the thin filaments and thereby the transfer and “integration” of the mechanical force generated in the elementary cycles. This aggregation is based principally or perhaps uniquely on structural properties of the tail segment. Proteolytic fragmentation derives its interest from the fact that by this means one can make a sort of “anatomy” of this part of the...