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The gated gait of the processive molecular motor, myosin V
Claudia Veigel1, Fei Wang, Marc L Bartoo
1Department of Biology, University of York, PO Box 373, York YO10 5YW, UK. cv1@york.ac.uk
Abstract:
Class V myosins are actin-based molecular motors involved in vesicular and organellar transport. Single myosin V molecules move processively along F-actin, taking several 36-nm steps for each diffusional encounter. Here we have measured the mechanical interactions between mouse brain myosin V and rabbit skeletal F-actin. The working stroke produced by a myosin V head is approximately 25 nm, consisting of two separate mechanical phases (20 + 5 nm). We show that there are preferred myosin binding positions (target zones) every 36 nm along the actin filament, and propose that the 36-nm steps of the double-headed motor are a combination of the working stroke (25 nm) of the bound head and a biased, thermally driven diffusive movement (11 nm) of the free head onto the next target zone. The second phase of the working stroke (5 nm) acts as a gate - like an escapement in a clock, coordinating the ATPase cycles of the two myosin V heads. This mechanism increases processivity and enables a single myosin V molecule to travel distances of several hundred nanometres along the actin filament.
Insights
Myosin V motors move along actin filaments using a 25 nm working stroke and a 11 nm diffusive step, coordinating their heads to travel long distances. This mechanism enhances processivity for efficient transport.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Class V myosins are essential actin-based molecular motors.
- They are crucial for intracellular transport of vesicles and organelles.
- Myosin V exhibits processive movement along actin filaments.
Purpose of the Study:
- To investigate the mechanical interactions between mouse brain myosin V and rabbit skeletal F-actin.
- To elucidate the step-size and coordination mechanism of myosin V motor activity.
Main Methods:
- Mechanical measurements of myosin V and F-actin interactions.
- Analysis of myosin V head movement and binding positions.
Main Results:
- Myosin V produces a 25 nm working stroke, divided into 20 nm and 5 nm phases.
- Preferred myosin V binding sites (target zones) exist every 36 nm on actin filaments.
- A model is proposed where 36 nm steps combine the working stroke and a diffusive movement of the free head.
Conclusions:
- The 5 nm phase of the working stroke acts as a gate, coordinating the two heads' ATPase cycles.
- This coordinated mechanism enhances myosin V processivity, enabling transport over hundreds of nanometers.