Abstract
A question remaining to be answered about RecA protein function concerns the role of ATP hydrolysis during the DNA-strand-exchange reaction. In this paper we describe the formation of joint molecules in the absence of ATP hydrolysis, using adenosine 5′-[γ-thio]triphosphate (ATP[γS]) as nucleotide cofactor. Upon the addition of double-stranded DNA, the ATP[γS]-RecA protein-single-stranded DNA presynaptic complexes can form homologously paired molecules that are stable after deproteinization. Formation of these joint molecules requires both homology and a free homologous end, suggesting that they are plectonemic in nature. This reaction is very sensitive to magnesium ion concentration, with a maximum rate and extent observed at 4-5 mM magnesium acetate. Under these conditions, the average length of heteroduplex DNA within the joint molecules is 2.4-3.4 kilobase pairs. Thus, RecA protein can form extensive regions of heteroduplex DNA in the presence of ATP[γS], suggesting that homologous pairing and the exchange of the DNA molecules can occur without ATP hydrolysis. A model for the RecA protein-catalyzed DNA-strand-exchange reaction that incorporates these results and its relevance to the mechanisms of eukaryotic recombinases are presented.
Original language | English (US) |
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Pages (from-to) | 21-25 |
Number of pages | 5 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 87 |
Issue number | 1 |
State | Published - 1990 |
Externally published | Yes |
Keywords
- DNA strand exchange
- Genetic recombination
- Homologous DNA pairing
- Three-stranded DNA intermediate
ASJC Scopus subject areas
- Genetics
- General