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Escherichia coli MutL loads DNA helicase II onto DNA
L E Mechanic1, B A Frankel, S W Matson
1Departments of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
The Journal of Biological Chemistry
|September 14, 2000
Summary
MutL protein binds DNA and facilitates the loading of UvrD (DNA helicase II) onto DNA, significantly enhancing DNA unwinding. This interaction is crucial for the methyl-directed mismatch repair pathway, though it doesn't increase processivity.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- MutL protein is known to interact with UvrD (DNA helicase II).
- MutL significantly stimulates UvrD's DNA unwinding activity within the mismatch repair pathway.
Purpose of the Study:
- To elucidate the mechanism by which MutL stimulates UvrD-catalyzed DNA unwinding.
- To investigate the roles of MutL-DNA and MutL-UvrD interactions in this stimulation.
Main Methods:
- DNA binding assays
- Single-turnover helicase assays
- DNA unwinding assays with long duplex substrates
Main Results:
- MutL binds to DNA and facilitates the loading of UvrD onto the DNA substrate.
- Both MutL-DNA and MutL-UvrD interactions are essential for stimulating UvrD's unwinding activity.
- MutL does not increase the processivity of UvrD unwinding as it does not clamp UvrD to the substrate.
Conclusions:
- MutL's stimulation of UvrD involves DNA binding and UvrD loading, not increased processivity.
- MutL acts as a master coordinator in the methyl-directed mismatch repair pathway by modulating helicase activity.
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