Affinity Cleavage of Double-Stranded DNA Directed by a RecA Nucleoprotein Filament Containing an Oligonucleotide-EDTA•Fe(II)
<p><i>Escherichia coli</i> RecA protein promotes strand exchange between two homologous DNAs by polymerizing on single-stranded DNA to form nucleoprotein filaments which then bind to a homologous sequence of duplex DNA. Joint formation between the RecA protein and three strands of...
| Summary: | <p><i>Escherichia coli</i> RecA protein promotes strand exchange between two homologous DNAs by polymerizing on single-stranded DNA to form nucleoprotein filaments which then bind to a homologous sequence of duplex DNA. Joint formation between the RecA protein and three strands of DNA is followed by strand exchange in which the original single strand is inserted into the duplex while the homologous duplex strand is displaced out. The structures of the strand exchange intermediates formed by the RecA protein have not been elucidated. We review studies aimed at determining such structures and we report the use of affinity cleaving techniques to probe the structure of the joint molecule formed between a RecA-oligonucleotide filament and duplex DNA by incorporating a thymidine-EDTA•Fe (T*) into the oligonucleotide of the filament. In our study, we find that the nucleoprotein filament binds antiparallel to the complementary strand within the homologous sequence of DNA and that it is associated more strongly with the complementary strand than with the homologous strand of the duplex.</p>
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