Different ability of novobiocin and coumermycin A1 to interact with nucleic acids

The possibility of two structurally related antibiotics, Coumermycin A1 and Novobiocin, to interact with nucleic acids was investigated. Only Coumermycin A1 was able to form complexes with DNA showing an apparent affinity constant comparable to that of the interaction with ribosomal RNA. A binding specificity for A + T complementary and repeating sequences was also exhibited by Coumermycin A1. In view of the different behaviour of the two compounds some considerations are made on their mode of action; although they are acting on the same target enzymes in Escherichia coli, they may affect the functions of eukaryotic cells through a different mechanism not equally specific and probably distinct for each of the two antibiotics.