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Magnesium regulates ADP dissociation from myosin V
Steven S Rosenfeld1, Anne Houdusse, H Lee Sweeney
1Department of Neurology, University of Alabama at Birmingham, FOT 1020, 1530 3rd Ave. South, Birmingham, AL 35294, USA. stevensr@uab.edu
The Journal of Biological Chemistry
|December 8, 2004
Summary
Mechanical strain in myosin V affects ADP release timing. Actin accelerates ADP release by lowering magnesium affinity, impacting motor velocity and ATPase activity.
Area of Science:
- Biochemistry
- Molecular Biology
- Muscle Physiology
Background:
- Myosin V processivity relies on mechanical strain influencing ADP release.
- The specific steps in ADP release affected by strain remain unclear.
- Understanding actin's role in myosin V ADP release kinetics is crucial.
Purpose of the Study:
- To investigate how magnesium regulates ADP release kinetics in myosin V.
- To determine the impact of actin on these ADP release pathways.
- To elucidate the mechanism by which mechanical strain modulates actin-myosin interactions.
Main Methods:
- Kinetic analysis of ADP release from purified myosin V.
- Examination of actomyosin V ATPase activity under varying magnesium concentrations.
- Characterization of magnesium and phosphate release steps.
Main Results:
- Actin accelerates ADP release from myosin V by decreasing the magnesium affinity of a myosin V-MgADP intermediate.
- This acceleration is linked to actin-induced structural changes in myosin, facilitating phosphate release.
- In actomyosin V, magnesium release precedes ADP release, and physiological magnesium levels slow ATPase activity and motor velocity.
Conclusions:
- Actin binding modulates myosin V's ADP release pathway through effects on magnesium affinity.
- Mechanical strain's influence on ADP release is explained by its modulation of actin-induced acceleration.
- Magnesium concentration is a key regulator of myosin V's ATPase activity and motor function.