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Unexpected structural diversity in DNA recombination: the restriction endonuclease connection
A B Hickman1, Y Li, S V Mathew
1Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA. ahickman@helix.nih.gov
Molecular Cell
|July 27, 2000
Summary
The Tn7 transposase uses two proteins for DNA transposition. Surprisingly, TnsA shares a fold with type II restriction enzymes, revealing a novel collaboration in DNA transposition.
Area of Science:
- Molecular Biology
- Genetics
- Structural Biology
Background:
- DNA transposition is a fundamental biological process involving coordinated DNA breakage and joining.
- The Tn7 transposase system utilizes two key proteins, TnsA and TnsB, to mediate transposition.
- TnsB belongs to the retroviral integrase superfamily, characterized by a conserved DDE motif.
Purpose of the Study:
- To determine the three-dimensional structure of the TnsA protein.
- To understand the structural basis of TnsA's role in Tn7 transposition.
- To elucidate the collaborative mechanism between TnsA and TnsB during transposition.
Main Methods:
- X-ray crystallography was employed to determine the structure of TnsA.
- High-resolution structural analysis was performed at 2.4 A.
Main Results:
- The determined structure of TnsA reveals a fold characteristic of type II restriction endonucleases.
- This finding was unexpected, as TnsA does not possess the canonical DDE motif found in TnsB.
- Tn7 transposition involves a functional partnership between a DDE-containing protein (TnsB) and a non-DDE protein with a restriction enzyme-like fold (TnsA).
Conclusions:
- The structural similarity of TnsA to type II restriction endonucleases expands the known functions of these protein folds.
- DNA transposition, specifically the Tn7 system, utilizes a collaborative mechanism involving proteins with distinct structural and functional domains.
- This study highlights the diverse biological roles accommodated by restriction enzyme-like structural motifs.
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