A physical model of ATP-induced actin-myosin movement in vitro

The nature of the mechanism limiting the velocity of ATP-induced unidirectional movements of actin-myosin filaments in vitro is considered. In the sliding process two types of "cyclic" interactions between myosin heads and actin are involved, i.e., productive and nonproductive. In the prod...

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Bibliographic Details
Published in:Biophysical journal 1991-02, Vol.59 (2), p.343-356
Main Authors: Tawada, K., Sekimoto, K.
Format: Article
Language:English
Subjects:
Actins - physiology
Adenosine Triphosphate - metabolism
Animals
Biological and medical sciences
Cell physiology
Fundamental and applied biological sciences. Psychology
Kinetics
Mathematics
Models, Biological
Molecular and cellular biology
Muscle Contraction
Myosins - metabolism
Myosins - physiology
Protein Binding
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Summary:The nature of the mechanism limiting the velocity of ATP-induced unidirectional movements of actin-myosin filaments in vitro is considered. In the sliding process two types of "cyclic" interactions between myosin heads and actin are involved, i.e., productive and nonproductive. In the productive interaction, myosin heads split ATP and generate a force which produces sliding between actin and myosin. In the nonproductive interaction "cycle," on the other hand, myosin heads rapidly attach to and detach from actin "reversibly," i.e., without splitting ATP or generating an active force. Such a nonproductive interaction "cycle" causes irreversible dissipation of sliding energy into heat, because the myosin cross-bridges during this interaction are passive elastic structures. This consideration has led us to postulate that such cross-bridges, in effect, exert viscous-like frictional drag on moving elements. Energetic considerations suggest that this frictional drag is much greater than the hydrodynamic viscous drag. We present a model in which the sliding velocity is limited by the balance between the force generated by myosin cross-bridges in the productive interaction and the frictional drag exerted by other myosin cross-bridges in the nonproductive interaction. The model is consistent with experimental findings of in vitro sliding, including the dependence of velocity on ATP concentration, as well as the sliding velocity of co-polymers of skeletal muscle myosin and phosphorylated and unphosphorylated smooth muscle myosins.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(91)82228-7