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Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
Human myosin Vc is a low duty ratio nonprocessive motor
Shinya Watanabe1, Tomonobu M Watanabe, Osamu Sato
1Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
The Journal of Biological Chemistry
|December 15, 2007
Summary
Myosin Vc, unlike other myosin V isoforms, operates as a nonprocessive motor. Its distinct ATPase cycle and weak actin binding suggest unique cargo transport mechanisms.
Area of Science:
- Molecular Biology
- Biochemistry
- Cell Biology
Background:
- Vertebrates possess three myosin V isoforms (Va, Vb, Vc) involved in distinct membrane trafficking.
- Myosin Va and Vb are known high duty ratio, processive motors.
Purpose of the Study:
- To elucidate the ATPase cycle mechanism of myosin Vc.
- To compare the motor properties of myosin Vc with other myosin V isoforms.
Main Methods:
- Biochemical assays to determine kinetic parameters (K(ATPase), ADP release rate, P(i) burst size).
- Kinetic modeling to understand the ATPase cycle.
- Total internal reflection fluorescence microscopy to assess processivity.
Main Results:
- Myosin Vc exhibits a significantly higher K(ATPase) (62 µM) compared to myosin Va (~1 µM).
- ADP release rate (12.7 s⁻¹) exceeds the overall ATPase cycle rate (6.5 s⁻¹).
- Myosin Vc spends most of its ATPase cycle in a weak actin binding state and is a nonprocessive motor.
Conclusions:
- Myosin Vc's ATPase mechanism differs substantially from myosin Va and Vb.
- Myosin Vc functions as a nonprocessive motor, utilizing distinct mechanisms for cargo transport.
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