Model of the interactions of calichemicin gamma 1 with a DNA fragment from pBR322.

An analysis of the binding interactions of several DNA-drug complexes that utilize carbohydrates for DNA recognition has been undertaken. It is proposed that the carbohydrate residues function as general minor groove binding elements, and the stereochemistry of aglycone attachment sites is generally disposed to promote a right-handed helical geometry that is complementary to right-handed DNA. The constitution and stereochemistry of the DNA double-strand cleaving agent calichemicin gamma 1 is consistent with this analysis. Docking experiments with computer-generated models of this drug and a dodecamer duplex that was found to serve as a calichemicin cleavage site were performed to gain insight into the origin of the drug's sequence-selective binding and cutting properties. A model is presented that provides a molecular level understanding of the double-strand cleavage patterns that result from the action of calichemicin gamma 1 on DNA.