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The duplex DNA is very underwound in the three-stranded RecA protein-mediated synaptic complex
O N Voloshin1, R D Camerini-Otero
1Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Health, Bethesda, MD 20892-1810, USA.
Summary
Researchers studied the RecA protein
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- RecA protein is crucial for bacterial homologous recombination.
- It facilitates DNA homology searching and synaptic complex formation.
- The precise architecture of RecA-DNA complexes remains unclear.
Purpose of the Study:
- To investigate the structure of RecA protein-mediated DNA synapsis.
- To determine the topological parameters of three-stranded RecA-DNA complexes.
Main Methods:
- Chemical modification using potassium permanganate.
- Treatment of synaptic complexes with topoisomerase I.
- Analysis of linking number differences using agarose gel electrophoresis.
Main Results:
- RecA-mediated synaptic complexes exhibit distinct topology compared to deproteinized D-loops.
- The DNA duplex within the complex is unwound to approximately 27 base pairs per helical turn.
- Chemical footprinting suggests an extended, unwound, three-stranded helical structure.
Conclusions:
- This study provides the first quantitative topological data for RecA-mediated three-stranded synaptic complexes.
- The structure of these complexes differs significantly from simple D-loops.