Abstract
Skeletal muscle contraction is a canonical example of motor-driven
force generation. Despite the long history of research in this topic,
a mechanistic explanation of the collective myosin force generation
is lacking. We present a theoretical model of muscle contraction
based on the conformational movements of individual myosins and experimentally
measured chemical rate constants. Detailed mechanics of the myosin
motor and the geometry of the sarcomere are taken into account. Two
possible scenarios of force generation are examined. We find only
one of the scenarios can give rise to a plausible contraction mechanism.
We propose that the synchrony in muscle contraction is due to a force-dependent
ADP release step. Computational results of a half sarcomere with
150 myosin heads can explain the experimentally measured force-velocity
relationship and efficiency data. We predict that the number of working
myosin motors increases as the load force is increased, thus showing
synchrony among myosin motors during muscle contraction. We also
find that titin molecules anchoring the thick filament are passive
force generators in assisting muscle contraction.
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