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How occasional backstepping can speed up a processive motor protein
1Department of Physics, East Carolina University, Greenville, NC 27858, USA. bierm@ecu.edu
Bio Systems
|November 25, 2010
Summary
Motor protein kinesin’s accidental backsteps are key to its speed. Increased backstepping enhances entropy and reduces free energy, optimizing kinesin’s catalytic cycle for maximum forward motion.
Area of Science:
- Molecular Biology
- Biophysics
- Biochemistry
Background:
- Motor protein kinesin moves along microtubules, powered by ATP hydrolysis.
- Kinesin exhibits a higher-than-expected rate of accidental backsteps.
- These backsteps deviate from a simple reversal of the forward stepping cycle.
Purpose of the Study:
- To develop a model incorporating kinesin's backstep transition.
- To investigate the impact of backstepping on kinesin's energy landscape and dynamics.
- To determine if backstepping contributes to kinesin's efficiency and evolutionary optimization.
Main Methods:
- Development of a simple effective model for kinesin stepping.
- Analysis of the model to understand the role of backstep transitions.
- Thermodynamic and kinetic analysis of the proposed model.
Main Results:
- Backstepping increases the entropy of the final and activation states, reducing their free energy.
- This free energy reduction accelerates the kinesin catalytic cycle, increasing both forward and backward step rates.
- Maximal net forward speed is achieved at a non-zero backstep percentage.
Conclusions:
- Kinesin's backstepping mechanism is crucial for optimizing its speed.
- The observed backstep percentage in kinesin aligns with the optimal value predicted by the model.
- Natural selection may have favored kinesin's evolution towards maximal speed through this backstepping mechanism.
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