3-substituted coumarin derivatives over-activate the HslV protease: A potential drug target for antibacterial...

The bacterial HslVU complex consists of two different proteins, i.e., the HslV protease and the HslU ATPase. The functional HslVU enzyme complex forms only when the HslU c-terminal helix is inserted into the cavity located between two adjacent HslV monomers in order to allosterically activate the HslV protease. Based on its essential role in maintaining microbial proteostasis as well its absence from human beings, it is considered a promising therapeutic target for designing antibacterial agents. The goal of the present study was to find out potential drug candidates that could over-activate the HslV protease and produce aberrant proteolysis in pathogenic bacteria. Derivatives of 3-substituted coumarin have been identified as potential HslV protease activators based on their highest docking scores, ideal interaction patterns, and significant in-vitro HslV activation potential. Their ED⁵⁰ values were in the sub-micromolar range, i.e., 0.4-0.48µM. The conformational stability of the contacts between the HslV dimer and the active compounds was further confirmed by molecular dynamics studies. Correspondingly, the ADMET characteristics of these lead molecules considerably demonstrated their significant non-toxic drug-like abilities. This research not only identified small non-peptidic HslV protease activators but also improved the understanding of the mode of action of 3-substituted coumarin derivatives as antibacterials.