Abstract
Selective hits for the glutaredoxin ortholog of Brucella melitensis are determined using STD NMR and verified by trNOE and 15N-HSQC titration. The most promising hit, RK207, was docked into the target molecule using a scoring function to compare simulated poses to experimental data. After elucidating possible poses, the hit was further optimized into the lead compound by extension with an electrophilic acrylamide warhead. We believe that focusing on selectivity in this early stage of drug discovery will limit cross-reactivity that might occur with the human ortholog as the lead compound is optimized. Kinetics studies revealed that lead compound 5 modified with an ester group results in higher reactivity than an acrylamide control; however, after modification this compound shows little selectivity for bacterial protein versus the human ortholog. In contrast, hydrolysis of compound 5 to the acid form results in a decrease in the activity of the compound. Together these results suggest that more optimization is warranted for this simple chemical scaffold, and opens the door for discovery of drugs targeted against glutaredoxin proteins—a heretofore untapped reservoir for antibiotic agents.
Highlights
Fragment-Based Drug Discovery (FBDD) is an emerging method for screening ligands against putative drug target proteins [1]
A library of 463 small fragment compounds was screened for selectivity against two orthologous glutaredoxin proteins, with the rationale that affinity for selective hits may be amplified with chemical synthesis while conserving ortholog specificity
This study aims to probe these differences to identify a fragment specific for BrmGRX and to modify that fragment into a lead warhead using an electrophilic group
Summary
Fragment-Based Drug Discovery (FBDD) is an emerging method for screening ligands against putative drug target proteins [1]. The goal of the work that follows was applying FBDD techniques to discover and develop a medicinally significant lead molecule with selectivity for a bacterial glutaredoxin while avoiding cross reactivity with the human ortholog. The primary method for discovering prospective leads is a variant of Saturation Transfer Difference (STD) NMR. A library of 463 small fragment compounds was screened for selectivity against two orthologous glutaredoxin proteins, with the rationale that affinity for selective hits may be amplified with chemical synthesis while conserving ortholog specificity. Fragments serve the role of lead molecules to guide development of drug compounds that selectively target the protein of a particular infectious species with reduced likelihood of off-target interactions with host proteins
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