PERIODICITY IN RECA PROTEIN-DNA COMPLEXES

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 obtaine d demonstrate a similarity of DNA states in the complexes with recA pr otein formed as a result of recA promoted strand exchange and renatura tion reactions. The guanine modification efficiency varies periodicall y as a function of the base position along the oligonucleotide axis, w ith a period of 3 nucleotides. This effect suggests that the arrangeme nt of recA monomers along the oligonucleotide is strictly ordered, and the dimethylsulfate reactivity of a guanine residue depends on the si te of its binding in a recA monomer. (C) 1997 Federation of European B iochemical Societies.