Periodicity in recA protein-DNA complexes

Abstract

The reaction of guanine residues with dimethylsulfate was studied for complexes of recA protein with fluorescent dye tagged double stranded oligonucleotides. The patterns of dimethylsulfate modification obtained demonstrate a similarity of DNA states in the complexes with recA protein formed as a result of recA promoted strand exchange and renaturation reactions. The guanine modification efficiency varies periodically as a function of the base position along the oligonucleotide axis, with a period of 3 nucleotides. This effect suggests that the arrangement of recA monomers along the oligonucleotide is strictly ordered, and the dimethylsulfate reactivity of a guanine residue depends on the site of its binding in a recA monomer.