Sequence-specific recognition of B-DNA by oligo(N-methylpyrrolecarboxamide)s

Abstract

Four homologous oligopeptide-EDTA molecules, tri-, tetra, penta-, and hexa(N-methylpyrrolecarboxamide)-EDTA, in the presence of Fe(II), O2, and dithiothreitol, cleave (32)P-end-labeled restriction fragments from plasmid pBR322 DNA at common locations rich in A·T base pairs that differ in the size of the binding site. From analysis of the cleavage patterns visualized by high-resolution denaturing gel electrophoresis, the oligopeptides with three, four, five, and six N-methylpyrrolecarboxamide units, containing four, five, six, and seven amide NHs, bind sites of A·T-rich DNA consisting of five, six, seven, and eight contiguous base pairs, respectively. The general rule of n amides affording binding site sizes of n + 1 base pairs is consistent with the oligopeptides binding in the minor groove of right-handed DNA, with the amide NH groups forming bridges between the adjacent N-3 and O-2 atoms of adenine or thymine on opposite strands of the DNA helix.

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