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Topoisomerase IV bends and overtwists DNA upon binding
G Charvin1, T R Strick, D Bensimon
1Laboratoire de Physique Statistique, Ecole Normale Supérieure, UMR 8550 Centre National de la Recherche Scientifique, Paris, France. gcharvin@rockefeller.edu
Biophysical Journal
|May 3, 2005
Summary
Escherichia coli topoisomerase IV (Topo IV) binds cooperatively to supercoiled DNA, preferentially to positively supercoiled DNA. This study reveals insights into Topo IV
Area of Science:
- Molecular Biology
- Biochemistry
- Structural Biology
Background:
- Escherichia coli topoisomerase IV (Topo IV) is crucial for DNA replication, unlinking sister chromosomes.
- Topo IV efficiently resolves positive supercoils but not negative ones.
Purpose of the Study:
- To investigate the DNA binding properties of Topo IV in the absence of ATP.
- To characterize the interaction dynamics and structural changes induced by Topo IV binding.
Main Methods:
- Single-molecule micromanipulation setup.
- Analysis of cooperative binding, DNA bending, and interaction dynamics.
Main Results:
- Topo IV exhibits cooperative binding to supercoiled DNA (Hill coefficient ~4), indicating subunit assembly.
- Preferential binding to (+) supercoiled DNA over (-) supercoiled DNA.
- Topo IV bends DNA and alters its twist/writhe, with dynamics alternating between weakly and strongly bound states.
Conclusions:
- The study elucidates the mechanism of Topo IV binding to DNA, highlighting its preference for supercoiled structures.
- The developed methodology offers a general approach for studying other DNA-protein interactions.
- Findings contribute to understanding DNA topology regulation by topoisomerases.
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