RecA protein plays a pivotal role in homologous recombination inEscheri-chia coli. RecA polymerizes on single-stranded (ss) DNA forming a nucleo-protein filament. Then double-stranded (ds) DNA is bound and searched for segments homologous to the ssDNA. Finally, homologous strands are exchanged, a new DNA duplex is formed, and ssDNA is displaced. We report a quantitative analysis of RecA interactions with ss d(pN)n of var-ious structures and lengths using these oligonucleotides as inhibitors of RecA filamentation on d(pT)20
