Demonstration of mechanochemical coupling in systems containing actin, ATP and non aggregating active myosin derivatives

Solutions of heavy meromyosin (HMM) induced active streaming when introduced into fine capillaries together with actin and adenosine triphosphate (ATP). 'Ghost' myofibrils, obtained by the selective extraction of myosin, contracted by irrigation with HMM or with the water soluble myosin derivative poly DL alanyl myosin, followed by the addition of ATP. It is concluded that filament formation by myosin is not a prerequisite for mechanochemical coupling in actomyosin systems. It is suggested that, in living muscle, the contractile force is generated by the interaction with actin of both myosin filaments and myosin oligomers and/or monomers; the latter may be responsible for the 'residual tension' observed in isometrically contracting muscles which have been stretched to a point of no overlap between the 2 sets of filaments. Since both nonaggregating myosin derivatives do not exhibit superprecipitation, it is proposed that the absence of superprecipitation should not be taken as an indication of the nonexistence of mechanochemical transduction.