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Structural insights into single-stranded DNA binding and cleavage by F factor TraI
Saumen Datta1, Chris Larkin, Joel F Schildbach
1Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.
Structure (London, England : 1993)
|November 8, 2003
Summary
Bacterial conjugation, crucial for antibiotic resistance spread, involves relaxase proteins. We determined the F plasmid TraI relaxase structure, revealing a unique active site for DNA cleavage.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbiology
Background:
- Conjugative plasmid transfer is a key mechanism for bacterial genome diversification and the spread of antibiotic resistance.
- Relaxase proteins are essential for initiating plasmid DNA cleavage during conjugation.
Purpose of the Study:
- To determine the three-dimensional structure of the F plasmid TraI relaxase domain.
- To elucidate the structural basis for the DNA cleavage activity of TraI relaxase.
Main Methods:
- X-ray crystallography was used to determine the structure of the F plasmid TraI relaxase domain.
- Bioinformatic analysis was performed to compare TraI with other known proteins.
Main Results:
- The F plasmid TraI relaxase domain adopts a unique fold with a five-strand beta sheet flanked by alpha helices, resembling circularly permuted AAV-5 Rep.
- A distinct DNA-binding cleft lined with neutral residues and unique Mg(2+) coordination involving three histidines were identified.
- The active site architecture suggests multiple roles for Mg(2+) in DNA cleavage via transesterification.
Conclusions:
- The determined structure provides novel insights into the mechanism of DNA cleavage by relaxases.
- The unique features of the TraI active site may explain its sequence specificity and catalytic efficiency.
- Understanding relaxase structure and function is critical for combating antibiotic resistance dissemination.