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Switching catalytic activity in the XerCD site-specific recombination machine
H Ferreira1, D Sherratt, L Arciszewska
1Division of Molecular Genetics, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
Journal of Molecular Biology
|September 8, 2001
Summary
The XerCD recombinase system converts circular DNA dimers to monomers. Removing N-terminal domains from XerC or XerD alters catalysis, impacting DNA recombination efficiency.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The XerCD recombinase system is crucial for resolving circular DNA dimers into monomers.
- This process involves a complex of XerC and XerD proteins acting on specific DNA sites.
- DNA strand exchange occurs sequentially, initiated by XerC and completed by XerD.
Purpose of the Study:
- To investigate the role of N-terminal domains in XerCD recombinase function.
- To determine how domain removal affects the catalytic activity and interaction of XerC and XerD.
- To identify the specific regions responsible for altered catalytic patterns in mutant recombinases.
Main Methods:
- Site-specific recombination assays using XerC and XerD variants.
- Construction of XerC and XerD mutants lacking N-terminal domains.
- Analysis of DNA strand exchange patterns and catalytic efficiency.
Main Results:
- XerC or XerD variants lacking N-terminal domains retain recombination activity with their wild-type partners.
- Removal of N-terminal domains alters the normal catalytic sequence, stimulating variant activity while impairing wild-type activity.
- Mutations in the alpha-helix B region of XerD are key determinants of this altered phenotype.
Conclusions:
- N-terminal domains of XerCD are important modulators of recombination catalysis, not essential for activity.
- Altered interactions within the XerCD heterotetramer due to domain removal affect Holliday junction substrate processing.
- This suggests a regulatory role for N-terminal domains in controlling the sequential nature of XerCD-mediated recombination.
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