Sep 6, 2012

Mechanical coupling between myosin molecules causes differences between ensemble and single-molecule measurements

Biophysical Journal
Sam WalcottEdward P Debold

Abstract

In contracting muscle, individual myosin molecules function as part of a large ensemble, hydrolyzing ATP to power the relative sliding of actin filaments. The technological advances that have enabled direct observation and manipulation of single molecules, including recent experiments that have explored myosin's force-dependent properties, provide detailed insight into the kinetics of myosin's mechanochemical interaction with actin. However, it has been difficult to reconcile these single-molecule observations with the behavior of myosin in an ensemble. Here, using a combination of simulations and theory, we show that the kinetic mechanism derived from single-molecule experiments describes ensemble behavior; but the connection between single molecule and ensemble is complex. In particular, even in the absence of external force, internal forces generated between myosin molecules in a large ensemble accelerate ADP release and increase how far actin moves during a single myosin attachment. These myosin-induced changes in strong binding lifetime and attachment distance cause measurable properties, such as actin speed in the motility assay, to vary depending on the number of myosin molecules interacting with an actin filament. This ...Continue Reading

  • References52
  • Citations45

Citations

Mentioned in this Paper

ATP Binding
Muscle Rigidity
Cell Motility
Actins
Macromolecular Alteration
Myopathy
Smooth Muscle
Motility
Skeletal System
Phosphate Measurement

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