Nucleic Acids Research, 1980, Vol. 8, No. 5 1121-1132
© 1980
Articles |
Spectroscopic analysis of the equilibrium and kinetic DNA binding properties of several actinomycin analogs
Department of Pharmaceutical Chemistry, School of Pharmacy, University of California San Francisco, CA 94143, USA
Received November 30, 1979. Experiments are described that measure DNA dissociation kinetics and thermal denaturation temperatures for a series of actinomycin analogs containing, in the 3' amino acid position, pipecolic acid, proline or azetidine-2-carboxyiic acid. Also included are studies on actinomycin C3. Analysis of the temperature dependence of the slowest rate constant for DNA dissociation shows that both the enthalpy and entropy of activation increase as the ring size of the 3' amino acid decreases from six to five to four. All compounds increase the DNA melting temperature to the same extent except for the analog containing pipecolic acid, which shows a smaller effect. These results are discussed in terms of a possible role for conformational changes in the actinomycin pen-tapeptide lactone rings in determining the slow DNA dissociations rates for this class of intercalators. It is suggested that cis-trans isomerization of proline may be important in this regard.