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Evaluation of Cancer Stem Cell Migration Using Compartmentalizing Microfluidic Devices and Live Cell Imaging
Published on: December 23, 2011
Branch migration enzyme as a Brownian ratchet
Ivan Rasnik1, Yong-Joo Jeong, Sean A McKinney
1Physics Department, University of Illinois, Urbana-Champaign, Urbana, IL, USA. irasnik@physics.emory.edu
The EMBO Journal
|May 31, 2008
Summary
Helicases, like T7 gp4, may not actively unwind DNA. Instead, they act as Brownian ratchets, facilitating DNA branch migration by exploiting spontaneous random walks.
Area of Science:
- Molecular Biology
- Biochemistry
- Structural Biology
Background:
- Helicases traditionally unwind double-stranded nucleic acids.
- Mechanisms underlying helicase functions beyond unwinding are unclear.
Purpose of the Study:
- To investigate the mechanism of Holliday junction branch migration catalyzed by the ring-shaped helicase T7 gp4.
- To elucidate the role of helicase in DNA branch migration beyond simple unwinding.
Main Methods:
- Kinetic studies of Holliday junction branch migration.
- Single-molecule analysis to pinpoint stall positions.
Main Results:
- A single base heterology stalls helicase-catalyzed branch migration.
- Helicase presence promotes junction unfolding, accelerating spontaneous branch migration.
- Complex trajectories indicate random excursions of the branch point.
Conclusions:
- T7 gp4 helicase acts as a Brownian ratchet, not an active unwinder.
- Helicase facilitates and biases DNA branch migration directionally.
- This mechanism explains helicase functions beyond DNA unwinding.
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