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Electron microscopic visualization of RecT protein and its complexes with DNA
R J Thresher1, A M Makhov, S D Hall
1Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill 27599, USA.
Journal of Molecular Biology
|December 1, 1995
Summary
This study visualizes the Escherichia coli RecT protein and its DNA complexes using electron microscopy. RecT protein forms various structures and facilitates DNA strand exchange, crucial for DNA repair mechanisms.
Area of Science:
- Molecular Biology
- Structural Biology
- Microscopy
Background:
- The Escherichia coli RecT protein is involved in DNA strand exchange, a critical process for DNA repair.
- Understanding the structural organization of RecT protein and its interactions with DNA is essential for elucidating its function.
Purpose of the Study:
- To investigate the structural characteristics of the RecT protein alone and in complex with DNA substrates.
- To visualize the in vitro catalytic activity of RecT protein in DNA strand exchange.
Main Methods:
- Electron microscopy, specifically negative staining techniques, was employed.
- The study examined RecT protein monomers, oligomers, and nucleoprotein filaments formed with single-stranded and duplex DNA.
Main Results:
- RecT protein monomers form open C-shaped and closed O-shaped particles.
- Monomers assemble into donut-shaped oligomers (7-8 monomers) and rod-like structures.
- RecT forms 18 nm diameter, 10 nm pitch helical nucleoprotein filaments with single-stranded DNA.
- In the presence of RecE protein, RecT forms filamentous complexes on duplex DNA ends, leading to DNA cyclization.
Conclusions:
- RecT protein exhibits dynamic structural assembly, forming distinct particles and oligomers.
- RecT protein forms stable, twisted nucleoprotein filaments with ssDNA, indicating its role in DNA binding and processing.
- RecT, in conjunction with RecE, mediates DNA end modification and facilitates DNA cyclization through protein-protein interactions.