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The beta protein of phage lambda promotes strand exchange
1Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA.
Journal of Molecular Biology
|May 9, 1998
Summary
Bacteriophage lambda's beta protein facilitates DNA strand exchange by binding to single-stranded DNA and overcoming mismatches. This protein drives strand exchange directionally without requiring external energy sources like ATP.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Bacteriophage lambda encodes beta protein, a 28 kDa DNA-binding protein.
- Beta protein promotes the renaturation of complementary single DNA strands.
- Beta protein binds to single-stranded DNA and the renatured product, but not duplex DNA.
Purpose of the Study:
- To investigate the ability of beta protein to promote DNA strand exchange.
- To elucidate the mechanism by which beta protein drives strand exchange.
Main Methods:
- Examined beta protein's interaction with M13 circular single-stranded DNA and homologous oligonucleotide.
- Assessed beta protein's ability to facilitate strand exchange in the presence of DNA mismatches.
- Analyzed the polarity and energy requirements of the strand exchange reaction.
Main Results:
- Beta protein mediated the replacement of an annealed oligonucleotide by a homologous longer strand on M13 DNA.
- Beta protein facilitated strand exchange through 4-8 mismatches, which blocked spontaneous reactions.
- The reaction exhibited polarity, and beta protein remained bound to the heteroduplex product.
Conclusions:
- Beta protein possesses DNA strand exchange activity.
- Beta protein drives strand exchange directionally without ATP or other energy inputs.
- This reveals a novel mechanism for protein-driven DNA strand exchange.