On RecA protein-mediated homologous alignment of two DNA molecules. Three strands versus four strands.
The recA protein from Escherichia coli can homologously align two duplex DNA molecules; however, this interaction is much less efficient than the alignment of a single strand and a duplex. Three strand paranemic joints are readily detected. In contrast, duplex-duplex pairing is detected only when the incoming (second) duplex is negatively supercoiled, and even here the pairing is inefficient. The recA protein-promoted four strand exchange reaction is initiated in a three strand region, with efficiency increasing with the length of potential three strand pairing available for initiation. This indicates that a paranemic joint involving three DNA strands may be an important intermediate in all recA protein-mediated DNA strand exchange reactions and that the presence of three strands rather than four is a fundamental structural parameter of paranemic joints.
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706.
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Lindsley
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D001482:Base Composition; D003090:Coliphages / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D004279:DNA, Viral / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D008961:Models, Structural; D009690:Nucleic Acid Conformation; D011938:Rec A Recombinases / Q000378:metabolism*; D015183:Restriction Mapping; D013379:Substrate Specificity
D004277:DNA, Single-Stranded; D004279:DNA, Viral; D011938:Rec A Recombinases