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Many type IIs restriction endonucleases interact with two recognition sites before cleaving DNA
Abigail J Bath1, Susan E Milsom, Niall A Gormley
1Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom.
The Journal of Biological Chemistry
|December 1, 2001
Summary
Many type IIs restriction enzymes interact with two DNA recognition sites, often cleaving DNA more efficiently when two sites are present. Different mechanisms explain this enhanced DNA cleavage activity.
Area of Science:
- Molecular Biology
- Enzymology
Background:
- Type IIs restriction endonucleases are enzymes that recognize specific DNA sequences and cleave DNA strands at fixed distances from the recognition site.
- These enzymes are typically monomers that dimerize to perform DNA cleavage, potentially interacting with multiple recognition sequences.
Purpose of the Study:
- To investigate whether type IIs restriction enzymes interact with two copies of their recognition sequence during DNA cleavage.
- To explore the mechanisms and kinetics of DNA cleavage by type IIs enzymes when presented with single versus double recognition sites.
Main Methods:
- Type IIs restriction enzymes were tested using DNA substrates containing either one or two recognition sites.
- Cleavage rates and mechanisms were analyzed by comparing the enzymatic activity on one-site and two-site substrates.
Main Results:
- Most type IIs enzymes exhibited faster DNA cleavage with two recognition sites compared to one.
- Observed mechanisms included sequential cleavage at equal rates, rapid cleavage at one site followed by slower cleavage at the second, and concerted cleavage at both sites simultaneously.
- Some enzymes showed similar cleavage rates regardless of the number of recognition sites.
Conclusions:
- A significant number of type IIs restriction enzymes interact with two copies of their recognition sequence prior to or during DNA cleavage.
- This interaction can lead to enhanced cleavage efficiency through various mechanisms, including sequential or concerted cleavage.