Aminoactinomycin binding to DNA sequences lacking GpC sites: a thermodynamic and kinetic study

BIVER, T., M. VENTURINI, E. A. JARES-ERIJMAN, T. M. JOVIN AND F. SECCO

BIOCHEMISTRY

AMER CHEMICAL SOC

Año: 2009 vol. 48 p. 173 - 179

0006-2960

ABSTRACT: The interaction of 7-aminoactinomycin (7AAMD) with selected DNA sequences (TAGTTA, R5, HP5, and HP1) of different lengths and secondary structures, all containing a 5′-TAGT-3′ block, was studied at an ionic strength of 0.02 M and pH 7.7 by means of fluorescence equilibrium and kinetic (stopped-flow) measurements. Both approaches indicated that the antibiotic binds strongly to both the single-stranded and hairpin (HP1) structures, although the sequences lacked the canonical GpC sites favored by actinomycin. Binding isotherms and initial rate analyses revealed that the binding stoichiometry was 1:1 in all cases. While the single-stranded sequences displayed a simple monoexponential kinetic behavior, the binding of 7AAMD to HP1 at