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The specificity of the secondary DNA binding site of RecA protein defines its role in DNA strand exchange
Journal article   Open access

The specificity of the secondary DNA binding site of RecA protein defines its role in DNA strand exchange

A V Mazin and S C Kowalczykowski
Proceedings of the National Academy of Sciences - PNAS, v 93(20), pp 10673-10678
01 Oct 1996
PMID: 8855238
url
https://doi.org/10.1073/pnas.93.20.10673View
Published, Version of Record (VoR) Open

Abstract

Rec A Recombinases - metabolism Recombination, Genetic DNA, Single-Stranded - metabolism Escherichia coli Protein Binding Substrate Specificity DNA - metabolism Deoxyribonucleoproteins - metabolism
The RecA protein-single-stranded DNA (ssDNA) filament can bind a second DNA molecule. Binding of ssDNA to this secondary site shows specificity, in that polypyrimidinic DNA binds to the RecA protein-ssDNA filament with higher affinity than polypurinic sequences. The affinity of ssDNA, which is identical in sequence to that bound in the primary site, is not always greater than that of nonhomologous DNA. Moreover, this specificity of DNA binding does not depend on the sequence of the DNA bound to the RecA protein primary site. We conclude that the specificity reflects an intrinsic property of the secondary site of RecA protein rather than an interaction between DNa molecules within nucleoprotein filament--i.e., self-recognition. The secondary DNA binding site displays a higher affinity for ssDNA than for double-stranded DNA, and the binding of ssDNA to the secondary site strongly inhibits DNA strand exchange. We suggest that the secondary binding site has a dual role in DNA strand exchange. During the homology search, it binds double-stranded DNA weakly; upon finding local homology, this site binds, with higher affinity, the ssDNA strand that is displaced during DNA strand exchange. These characteristics facilitate homologous pairing, promote stabilization of the newly formed heteroduplex DNA, and contribute to the directionality of DNA strand exchange.

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Biochemistry & Molecular Biology
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