Distamycin A and its analogs as agents for blocking of endo R. EcoRI activity.

Distamycin A (Dst) and its analogs protect the lambda phage DNA from cleavage with endoR. EcoRI and show selective affinity for different recognition sites of endoR. EcoRI on this DNA producing enlarged DNA fragments of various composition and length. The affinity of the antibiotic for DNA is influenced by the number of pyrrol carboxamide units in Dst molecule and does not strongly depend on the substitution of the N-methyl group by the N-propyl one. Since in the complex with DNA the antibiotics of the Dst type are localized in its minor groove a conclusion can be made that the minor groove of DNA is needed for the interaction of the restriction endonuclease with DNA.