Binding of Telomestatin to a Telomeric G-Quadruplex DNA Probed by All-Atom Molecular Dynamics Simulations with Explicit Solvent

Telomestatin, a natural product isolated from Streptomyces anulatus, stabilizes telomeric DNA G-quadruplexes. Treatment with this ligand induces apoptosis of various cancer cells with a relatively low effect on somatic cells because of its high selectivity toward G-quadruplex over duplex DNA. A high-resolution structure of a G-quadruplex in complex with telomestatin does not yet exist because of its low solubility, and the binding nature of this ligand remains elusive. In this study, we utilized molecular binding simulations and MMGBSA binding energy analysis to decipher the nature of the binding of telomestatin to a telomeric G-quadruplex. We identified three major binding poses: bottom intercalation, top stacking, and groove binding. The top stacking mode resembles the pose observed in an NMR complex of the same G-quadruplex with the telomestatin analogue L2H. The bottom intercalation and groove binding poses were not observed in the previous studies of L2H. The bottom intercalation mode exhibited the most favorable binding energy among the three modes, while also partially intercalating into the telomeric quadruplex. The dynamic and energetic properties of these three binding modes are thoroughly examined. "Flip insertion" and "slide insertion" were observed in the bottom intercalation mode. Our findings also provide insight into the design of more selective DNA quadruplex ligands as anticancer agents in the future.