Echinomycin

Abstract

The story of echinomycin is of an antibiotic whose anti-cancer activity was rediscovered thanks to scientific investigation of its mode of action at the molecular level. It was the first DNA bis-intercalator identified (in 1974). Molecular models for echinomycin and its congeners are now well-founded on crystallographic data. These are beginning to throw light on significant variations in conformation which affect the ability of the antibiotics to recognise specific nucleotide sequences in DNA. Kinetic and other physical experiments have revealed much about the stability and selectivity of antibiotic-DNA complexes: stacking forces are important, as are hydrogen bonding interactions. Echinomycin preferentially recognises sites in DNA containing the CpG step, but other sites of lower occupancy exist and the antibiotic can migrate between them. Currently a good deal of attention is being paid to the suggestion that echinomycin might change Watson-Crick base pairs to a Hoogsteen form.