Nordén, Bengt and Wittung-Stafshede, Pernilla and Ellouze, Christine and Kim, Hye-Kyung and Mortensen, Kell and Takahashi, Masayuki (1998) Base Orientation of Second DNA in RecA·DNA Filaments. Analysis by combination of linear dichroism and small angle neutron scattering in flow-oriented solution. Journal of Biological Chemistry, 273 (25). pp. 15682-15686. ISSN 0021-9258 http://resolver.caltech.edu/CaltechAUTHORS:NORjbc98
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To gain insight into the mechanism of pairing two complementary DNA strands by the RecA protein, we have determined the nucleobase orientation of the first and the second bound DNA strands in the RecA·DNA filament by combined measurements of linear dichroism and small angle neutron scattering on flow-oriented samples. An etheno-modified DNA, poly(depsilon A) was adapted as the first DNA and an oligo(dT) as the second DNA, making it possible to distinguish between the linear dichroism signals of the two DNA strands. The results indicate that binding of the second DNA does not alter the nucleobase orientation of the first bound strand and that the bases of the second DNA are almost coplanar to the bases of the first strand although somewhat more tilted (60 degrees relative to the fiber axis compared with 70 degrees for the first DNA strand). Similar results were obtained for the RecA·DNA complex formed with unmodified poly(dA) and oligo(dT). An almost coplanar orientation of nucleobases of two DNA strands in a RecA-DNA filament would facilitate scanning for, and recognition of, complementary base sequences. The slight deviation from co-planarity could increase the free energy of the duplex to facilitate dissociation in case of mismatching base sequences.
|Additional Information:||Copyright © 1998 by The American Society for Biochemistry and Molecular Biology, Inc. This work has been supported by grants from the European Community (BioMed program) and French Ministry of Education (ACC-SDV) and by Institut Curie and the French and Swedish Research Councils (CNRS and NFR).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. [C.E. was a] [r]ecipient of fellowships from the Association pour la Recherche sur le Cancer and the French government.|
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