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Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
Two single-headed myosin V motors bound to a tetrameric adapter protein form a processive complex
Elena B Krementsova1, Alex R Hodges, Carol S Bookwalter
1Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA.
The Journal of Cell Biology
|November 16, 2011
Summary
Yeast Myo4p motors become processive when bound to mRNA-binding protein She2p, enabling efficient transport. This cargo-driven processivity mimics dimeric motors, crucial for cellular functions.
Area of Science:
- Cell biology
- Molecular motor function
- Protein-protein interactions
Background:
- Myo4p is a class V myosin in yeast responsible for continuous mRNA transport.
- Myo4p is nonprocessive in vitro, but its in vivo function suggests regulated processivity.
- The adapter protein She3p forms a single-headed Myo4p-She3p complex.
Purpose of the Study:
- To investigate how Myo4p achieves processive transport.
- To elucidate the role of the mRNA-binding protein She2p in Myo4p motor activity.
- To characterize the structural and functional basis of Myo4p-She2p complex formation.
Main Methods:
- Biochemical assays to characterize motor complex formation.
- In vitro motility assays on actin-tropomyosin filaments.
- Mapping of protein binding sites.
Main Results:
- Two Myo4p-She3p motors bind to the tetrameric She2p, forming a processive double-headed complex.
- She3p binds to a specific α helix on She2p.
- Processive motility of Myo4p-She2p complexes was observed on actin filaments.
- Motor activity and processivity are regulated by cargo (She2p) binding.
- Each Myo4p head takes ~72 nm steps in a hand-over-hand manner.
Conclusions:
- Cargo binding by She2p converts nonprocessive Myo4p motors into a processive complex.
- This cargo-mediated regulation is essential for efficient mRNA transport in yeast.
- The coupled motor system exhibits properties similar to dimeric processive motors like vertebrate myosin Va.
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