Mechanism of Action of Chromomycin A3
III. On the Binding of Chromomycin A3 with DNA and Physicochemical Properties of the Complex
1968 Volume 63 Issue 5 Pages 566-572
Details
1968 Volume 63 Issue 5 Pages 566-572
1. A shift of the absorption maximum of chromomycin A3 at 406 mμ toward longer wavelengths was found in the presence of Mg++ or other bivalent cations such as Mn++, Co++ and Ni++. Both ultraviolet and visible absorption bands of chromomycin A3 were intensified by the addition of Mg++.
2. Native and heat-denatured calf thymus DNA and yeast tRNA did not show any effect on the spectrum of the antibiotic both in the presence and in the absence of Mg++.
3. In the presence of Mg++, the thermal transition curve of calf thymus DNA shifted toward higher temperatures on addition of the antibiotic.
4. The Mg++ requirement for binding of chromomycin A3 with DNA was demonstrated by the fact that DNA precipitated by ethanol was yellow in the presence of Mg++ but white in its absence and that the absorption of the supernatant at 406 mμ decreased in the presence of Mg++ but not in its absence.
5. The sugar moiety of chromomycin A3 was necessary for binding of the antibiotic with DNA, because chromomycinone did not co-precipitated with calf thymus DNA in the presence of Mg++.
6. Chromomycin A3 co-sedimented with DNA only in the presence of Mg++ as examined by ultracentrifugation in a sucrose solution.
