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Rapid double 8-nm steps by a kinesin mutant
Hideo Higuchi1, Christian Eric Bronner, Hee-Won Park
1Department of Metallurgy and Center for Interdisciplinary Research, Tohoku University, Sendai, Japan.
The EMBO Journal
|July 17, 2004
Summary
A kinesin motor mutation reveals its walking mechanism. Under high force, the motor takes 16-nm steps, showing an asymmetric cycle crucial for understanding kinesin
Area of Science:
- Molecular motor function
- Cellular mechanics
- Biophysics
Background:
- The process of kinesin motor proteins walking along microtubules is not fully understood.
- It is hypothesized to involve alternating head binding and ATP hydrolysis.
- A single amino acid change was investigated for its effect on kinesin's motor function.
Purpose of the Study:
- To investigate the effect of a specific amino acid mutation on kinesin motor stepping.
- To elucidate the underlying mechanism of kinesin's processive movement along microtubules.
- To explore the role of nucleotide hydrolysis and load in kinesin's walking cycle.
Main Methods:
- Single-motor laser-trap assays were employed to measure kinesin movement.
- Experiments were conducted under varying force and ATP concentration conditions.
- The stepping behavior of a mutant kinesin motor was analyzed at the nanometer scale.
Main Results:
- The mutation did not alter the basic 8-nm stepping mechanism under low force or ATP.
- Under high force, the mutant kinesin exhibited 16-nm displacements, resolving into double 8-nm steps.
- Alternating short and long dwells were observed under high force, indicating an asymmetric stepping cycle.
Conclusions:
- The findings support an asymmetric two-headed walking model for kinesin.
- Cooperative interactions between the two kinesin heads are suggested.
- ADP release may be a force-producing event in the kinesin walking cycle.