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Structural and thermodynamic studies of the interaction of distamycin A with the parallel quadruplex structure [d(TGGGGT)]4.

Martino L, Virno A, Pagano B, Virgilio A, Di Micco S, Galeone A, Giancola C, Bifulco G, Mayol L, Randazzo A

Dipartimento di Chimica P. Corradini, Università degli Studi di Napoli Federico II, via Cintia, I-80126, Napoli, Italy.

The complex between distamycin A and the parallel DNA quadruplex [d(TGGGGT)]4 has been studied by 1H NMR spectroscopy and isothermal titration calorimetry (ITC). To unambiguously assert that distamycin A interacts with the grooves of the quadruplex [d(TGGGGT)]4, we have analyzed the NMR titration profile of a modified quadruplex, namely [d(TGGMeGGT)]4, and we have applied the recently developed differential frequency-saturation transfer difference (DF-STD) method, for assessing the ligand-DNA binding mode. The three-dimensional structure of the 4:1 distamycin A/[d(TGGGGT)]4 complex has been determined by an in-depth NMR study followed by dynamics and mechanics calculations. All results unequivocally indicate that distamycin molecules interact with [d(TGGGGT)]4 in a 4:1 binding mode, with two antiparallel distamycin dimers that bind simultaneously two opposite grooves of the quadruplex. The affinity between distamycin A and [d(TGGGGT)]4 enhances ( approximately 10-fold) when the ratio of distamycin A to the quadruplex is increased. In this paper we report the first three-dimensional structure of a groove-binder molecule complexed to a DNA quadruplex structure.

Published 20 December 2007 in J Am Chem Soc, 129(51): 16048-56.
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