title: Covalent DNA binding by vaccinia topoisomerase results in unpairing of the thymine base 5' of the scissile bond.
abstract: We have used potassium permanganate to probe contacts between vaccinia DNA topoisomerase and thymine residues in its 5'-CCCTT downward arrow DNA target site. Two major conclusions emerge from the experiments presented: (i) permanganate oxidation of the +2T base of the scissile strand interferes with topoisomerase binding to DNA, and (ii) the +1T base of the scissile strand becomes unpaired upon formation of the covalent topoisomerase-DNA intermediate. Disruption of T:A base pairing is confined to the +1-position. Covalently bound DNAs that have experienced this structural distortion (such DNAs being marked by oxidation at +1T) are fully capable of being religated. We suggest that a protein-induced DNA conformational change is a component of the strand passage step of the topoisomerase reaction.
authors.affiliation: Molecular Biology Program, Sloan-Kettering Institute, New York, New York 10021, USA.
authors.forename: J
authors.initials: J
authors.lastname: Sekiguchi
authors.forename: S
authors.initials: S
authors.lastname: Shuman
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D006868:Hydrolysis; D015335:Molecular Probes; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011196:Potassium Permanganate; D011485:Protein Binding; D013941:Thymine / Q000378:metabolism*; D014616:Vaccinia virus / Q000201:enzymology*
chemical_list: D015335:Molecular Probes; D011196:Potassium Permanganate; D004247:DNA; D004264:DNA Topoisomerases, Type I; D013941:Thymine