Myosin aggregates as a requirement for contraction and a proposal to the mechanism of contraction of actomyosin systems.

Glycerinated fibers of rabbit psoas muscle showed no augmentation of tension development upon incubation with heavy meromyosin, irrespective of whether the fibers were of standard length, stretched, or extracted of their myosin content. The effect of heavy meromyosin was to suppress contraction. These observations are in disagreement with certain recent published reports (Oplatka et al., 1974) and do tend to support the current sliding filament theory of muscle contraction and the necessity of bipolar myosin filaments for contraction. A possible mechanism of contraction in protein systems, including tension generation in actomyosin fibers and superprecipitation, is described emphasizing the polarity of both myosin and actin filaments.