BIOLOGICAL-ACTIVITY AND DNA-SEQUENCE SPECIFICITY OF SYNTHETIC CARBAMOYL ANALOGS OF DISTAMYCIN

A new penta(N-methylpyrrole carboxamide) analogue of the antibiotic di stamycin has been synthesized in which the N-terminal formylamino grou p was replaced by a carbamoyl moiety It was substantially more stable than distamycin in aqueous solution and bound to DNA with about the sa me affinity constant. It had an exemplary margin of selectivity agains t herpes simplex virus type 1-infected HEp-2 cells in culture compared to uninfected control cells, and was equipotent with distamycin. For comparison, data for analogues containing fewer N-methylpyrrole carbox amide units and/or lacking the carbamoyl replacement are presented. Ex tensive DNase I footprinting experiments were conducted and revealed t hat all the distamycin analogues bound to AT-rich nucleotide sequences in three different restriction fragments, irrespective of how many py rrole rings or which terminal moiety they contained. However, the rela tive strength of footprints differed significantly among the various c ompounds, though the apparent size of the binding site did not. With s emi-synthetic DNA containing inosine and 2,6-diaminopurine residues in place of guanosine and adenine, respectively, the compounds recognize d new binding sites composed of IC-rich clusters and were excluded fro m binding to their canonical sites. This showed that the process of sp ecific sequence recognition was critically dominated by the placement of the purine 2-amino group in the minor groove of the double helix.