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Investigation, by cross-linking, of conformational changes in F-actin during its interactions with myosin
Abstract:
The hypothesis that the subunits of F-actin rotate during interactin with myosin and ATP has been tested by using the specific cross-linking reagent p-phenylene-N,N'-bis(maleimide) (PM). The insertion of cross-links between F-actin subunits does not change the ability of the F-actin to activate the ATPase of either myosin subfragment-1 (S-1) or heavy meormyosin, and its ability to superprecipitate with myosin is unimpaired. We conclude that large-scale rotations of actin subunits are not required for activity. The cross-linking of F-actin by PM is, however, inhibited in a noncooperative fashion by S-1 binding, suggesting that a small local change in actin structure may accompany the binding of S-1 or that S-1 sterically blocks the cross-linking by binding near the contact region between actin subunits.
Insights
Large-scale rotations of actin subunits are not necessary for myosin interaction and ATP activity. Cross-linking F-actin with PM showed no impairment, suggesting localized structural changes upon myosin binding.
Area of Science:
- Biochemistry
- Molecular Biology
- Muscle Contraction
Background:
- Actin and myosin are key proteins in muscle contraction.
- The precise mechanism of actin subunit movement during myosin interaction is debated.
Purpose of the Study:
- To investigate whether F-actin subunits rotate during interaction with myosin and ATP.
- To determine the role of actin subunit rotation in myosin-activated ATPase activity.
Main Methods:
- Utilized p-phenylene-N,N'-bis(maleimide) (PM) as a specific cross-linking reagent for F-actin.
- Assessed the effect of F-actin cross-linking on myosin subfragment-1 (S-1) and heavy meromyosin ATPase activity.
- Evaluated the impact of cross-linking on F-actin's ability to superprecipitate with myosin.
Main Results:
- Cross-linking F-actin subunits with PM did not alter its ability to activate myosin ATPase.
- Superprecipitation of F-actin with myosin remained unimpaired after cross-linking.
- PM cross-linking of F-actin was inhibited by S-1 binding, indicating a noncooperative interaction.
Conclusions:
- Large-scale rotations of actin subunits are not essential for F-actin's functional activity with myosin.
- Myosin subfragment-1 binding may induce small, local structural changes in F-actin or sterically hinder cross-linking.
- The findings suggest a localized conformational change rather than global subunit rotation during actin-myosin interaction.