Structure-Based Ligandability Exploration of a G-Quadruplex-Forming Sequence from the Pseudomonas aeruginosa Genome

Bacterial G-quadruplexes (G4s) are related to survival and resistance mechanisms in several pathogens, making them attractive targets for innovative antimicrobials. However, little structural and ligand binding information is available so far. Based on the structure of the TET22 G4 from Pseudomonas aeruginosa, a structure-based multidisciplinary approach was applied here to assess its ligandability. A docking-based virtual screening allowed the identification of the putative TET22 groove binders 1–13 that were evaluated in biophysical and biological assays. Circular dichroism (CD) confirmed that compounds 1–13 and the reference ligand pyridostatin (PDS) bind and stabilize TET22, each displaying a differential preference for parallel or antiparallel/hybrid topology. Notably, compounds 5 and 7, the most effective ligands for TET22 G4, proved to be unable to stabilize a human telomeric G4 model used as a selectivity control. Microbiology evaluation returned weak efficacy for compounds 1–13, whereas a minimum inhibitory concentration (MIC) of 100 μM was obtained for the reference compound PDS, indicating that TET22 stabilization stronger than that provided by compounds 1–13 is required to observe a detectable antimicrobial efficacy. Surprisingly, some well-known human G4 binders were fully inactive.