Phosphate and ADP differently inhibit coordinated smooth muscle myosin groups
Lennart Hilbert1, Zsombor Balassy2, Nedjma B Zitouni3
1Department of Physiology, McGill University, Montréal, Québec, Canada; Centre for Applied Mathematics in Bioscience and Medicine, Montréal, Québec, Canada; Meakins-Christie Laboratories, Montréal, Québec, Canada.
Biophysical Journal
|February 5, 2015
Summary
Smooth muscle myosin
Area of Science:
- Biophysics
- Muscle Physiology
- Molecular Motors
Background:
- Actin filament motion is driven by myosin motors.
- Skeletal muscle myosin shows length-dependent actin sliding and arrest.
- Smooth muscle myosin's in vivo distribution suggests length-dependence is relevant.
Purpose of the Study:
- Investigate length-dependent actin arrest and sliding in smooth muscle myosin.
- Determine the effects of phosphate (Pi) and adenosine diphosphate (ADP) on smooth muscle myosin kinetics.
- Model myosin group kinetics to understand actin propulsion.
Main Methods:
- In vitro motility assays with smooth muscle myosin.
- Perturbation of individual myosin kinetics using physiological concentrations of Pi and ADP.
- Mathematical modeling of actin propulsion by myosin groups.
Main Results:
- Actin arrest and sliding were observed and dependent on actin length.
- Increased Pi reduced active sliding time, average velocity, and motile fraction.
- Increased ADP increased active sliding time but reduced velocity during sliding.
- Mathematical model simulations matched experimental data.
Conclusions:
- Smooth muscle myosin kinetics are inhibited by Pi and ADP.
- Pi and ADP concentrations modulate actin sliding and arrest phases.
- Myosin group chemical states explain actin arrest and sliding behaviors.
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