Análise bioquímica quântica do regulador TtgR e seus efetores

Abstract

The problem of cross-resistance to different classes of MDR (multidrug resistance) antibiotic has become a routine event in current medicine, implying therapeutic failure. Efflux pumps collaborate considerably for this resistance to antibacterial agents, the expression of such mechanisms is controlled by transcriptional regulators. TtgR is a multidrug binding regulator of the TtgABC pump, present in P. putida, it exhibits strong similarity to QacR, a multiple drug binding protein of S. aureus. We show here three crystallographic structures of TtgR, DOT strain T1E, in complex with the flavonoid Quercetin (QUE) and with the antibiotics Tetracycline (TAC) and Chloramphenicol (CLM). Through data with crystalline structures and computational simulations, it was possible to analyze the energetic contributions of these effectors to the general bonding site of TtgR using the Functional Density Theory (DFT) and the Molecular Fractionation Method with Conjugated Layers (MFCC). The results showed the energetic values of each amino acid residue constituting the interaction pocket with the ligands under analysis. This evaluation occurred within a radius of up to 13.0 Å away from the drugs. These effectors couple to the TtgR protein in a similar way, sharing a hydrophobic core, such as: LEU93, LEU92, ILE141, VAL171 and VAL96. It was observed some specific interactions with polar amino acids, such as ARG176, which became important for the TtgRQUE and TtgR-TAC complexes and HIS70 for the TtgR-TAC and TtgR-CLM complexes. This energetic characterization provides us with information relevant to understanding MDR resistance, concomitant with new possibilities in drug planning versus this mechanism of resistance.