Topography of the interaction of recA protein with single-stranded deoxyoligonucleotides.
recA protein, in the presence of adenosine 5'-(gamma-thio)triphosphate, formed stable complexes with single-stranded deoxyoligonucleotides between 9 and 20 residues in length but not with those 8-residues long. The binding of recA protein to a 15-mer and 20-mer completely protected the sugar-phosphate backbone of the nucleic acid from digestion by pancreatic deoxyribonuclease I and protected the 5'-terminal phosphate from cleavage by calf intestinal alkaline phosphatase. Ethylation of the phosphate backbone at any position by ethylnitrosourea blocked the binding of recA protein to the 15-mer but not to the 20-mer. Ethylation of phosphates near the ends of the 15-mer interfered less, suggesting a minimum binding site requirement. In contrast to the protection of the nucleic acid backbone, recA protein did not protect the N-7 position of guanine or the N-3 position of adenine from methylation by dimethyl sulfate, but rather enhanced the methylation of guanine. These results indicate that recA protein binds primarily to the phosphate backbone of single-stranded DNA, leaving the bases free for homologous pairing. We present a model for the organization of the presynaptic filament.
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D004277:DNA, Single-Stranded; D003850:Deoxyribonuclease I; D007700:Kinetics; D008961:Models, Structural; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011938:Rec A Recombinases / Q000378:metabolism*; D013329:Structure-Activity Relationship
D004277:DNA, Single-Stranded; D009838:Oligodeoxyribonucleotides; D011938:Rec A Recombinases; D003850:Deoxyribonuclease I