Biophys J, January 2001, p. 379-397, Vol. 80, No. 1

Link between the Enzymatic Kinetics and Mechanical Behavior in an Actomyosin Motor

Department of Physics, Faculty of Science, Kanazawa University, Kanazawa 920-1192, Japan

We have attempted to link the solution actomyosin ATPase with the mechanical properties of in vitro actin filament sliding over heavy meromyosin. To accomplish this we perturbed the system by altering the substrate with various NTPs and divalent cations, and by altering ionic strength. A wide variety of enzymatic and mechanical measurements were made under very similar solution conditions. Excellent correlations between the mechanical and enzymatic quantities were revealed. Analysis of these correlations based on a force-balance model led us to two fundamental equations, which can be described approximately as follows: the maximum sliding velocity is proportional to , where K_m^A is the actin concentration at which the substrate turnover rate is half of its maximum (V_max). The active force generated by a cross-bridge under no external load or under a small external load is proportional to . The equations successfully accounted for the correlations observed in the present study and observations in other laboratories.

Biophys J, January 2001, p. 379-397, Vol. 80, No. 1
© 2001 by the Biophysical Society   0006-3495/01/01/379/19  $2.00

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