[Actinomycin DO inhibition of RNA biosynthesis and its interaction with DNA preparations].

Actinomycin D0 differing from actinomycin D in replacement of I residue of sarcosine by glycine in one of the peptide chains was found to have a lower inhibitory effect on RNA synthesis in various biological systems. On interaction of E. coli with DNA actinomycin D0 formed a complex with DNA having the binding constant K=1.6 with 10-5 which was 100 times lower than the binding constant of actinomycin D. Therefore, actinomycin D0 formed a complex with DNA which was 100 times less stable than actinomycin D. Actinomycins D0, D and II having different conformations in buffer on interaction with DNA formed complexes having similar conformations. The conformational change from free actinomycin to bound actinomycin was found difficult in case of actinomycin D0 because of its slow rate of complex formation with DNA as compared to that of other actinomycins complex formation with DNA.