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Evidence for cleft closure in actomyosin upon ADP release
N Volkmann1, D Hanein, G Ouyang
1The Burnham Institute, La Jolla, California 92037, USA.
Nature Structural Biology
|December 2, 2000
Summary
Smooth muscle myosin
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Motors
Background:
- Understanding the molecular mechanisms of muscle contraction is crucial.
- Smooth muscle myosin and actin interactions are fundamental to muscle function.
Purpose of the Study:
- To elucidate the structural dynamics of the actomyosin complex during the muscle contraction cycle.
- To map conformational changes in myosin upon nucleotide binding and release.
Main Methods:
- Computer-based fitting of crystal structures into 3D reconstructions from electron cryomicroscopy.
- Mapping structural and dynamic changes in the actomyosin complex.
Main Results:
- Actomyosin structures in the presence and absence of MgADP differ significantly.
- MgADP release triggers a ~34 Å movement of the light chain binding domain and a ~9° rotation of the myosin motor domain.
- Cleft closure in the myosin head involves the upper 50 kDa region, stabilized by actin interactions.
Conclusions:
- A model is proposed where MgATP binding opens the myosin cleft, disrupting actin interaction and releasing myosin.
- These findings provide detailed structural insights into the myosin motor's power stroke mechanism.
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