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Biopolymers. 2001-2002;61(3):145-58.

The stretched DNA geometry of recombination and repair nucleoprotein filaments.

Author information

1
Department of Chemistry, Rice University, P. O. Box 1892, MS 65, Houston, TX 77005, USA. sfs@rice.edu

Abstract

The RecA protein of Escherichia coli plays essential roles in homologous recombination and restarting stalled DNA replication forks. In vitro, the protein mediates DNA strand exchange between single-stranded (ssDNA) and homologous double-stranded DNA (dsDNA) molecules that serves as a model system for the in vivo processes. To date, no high-resolution structure of the key intermediate, comprised of three DNA strands simultaneously bound to a RecA filament (RecA x tsDNA complex), has been elucidated by classical methods. Here we review the systematic characterization of the helical geometries of the three DNA strands of the RecA x tsDNA complex using fluorescence resonance energy transfer (FRET) under physiologically relevant solution conditions. Measurements of the helical parameters for the RecA x tsDNA complex are consistent with the hypothesis that this complex is a late, poststrand-exchange intermediate with the outgoing strand shifted by about three base pairs with respect to its registry with the incoming and complementary strands. All three strands in the RecA x tsDNA complex adopt extended and unwound conformations similar to those of RecA-bound ssDNA and dsDNA.

PMID:
11987178
DOI:
10.1002/bip.10145
[Indexed for MEDLINE]

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