Exploring Inhibition of Bacterial Conjugation Coupling Protein TrwB: Novel Ligands to Fight Antimicrobial Resistance Spread

Abstract

Bacterial conjugation is the most sophisticated mechanism for horizontal gene transfer. Conjugative plasmids allow the recipient bacterium to acquire new traits from the donor, such as antimicrobial resistance (AMR). Among the proteins involved in the plasmid transfer machinery, the Type IV Coupling Protein (T4CP) links the relaxosome and the Type IV Secretion System (T4SS). However, despite their biological relevance and their potential as a target to control AMR, only a few T4CPs have been exhaustively studied. The archetype of the T4CP family is the coupling protein of the conjugative plasmid R388, TrwB. The inhibition of TrwB ATPase activity or oligomerization with small-molecule modulators is expected to control the transfer of R388, contributing to combat AMR spread. Following a drug repurposing approach, we have combined in silico screening studies, molecular dynamics (MD) simulations, and in vitro bacterial conjugation assays to identify a small collection of compounds that selectively decrease the frequency of conjugation of the plasmid R388 (30–40%). Our results suggest that this inhibition is the result of the specific interaction of these drugs with TrwB. The search for conjugation inhibitors, via the inactivation of proteins such as T4CPs, rises as a strategy to advance in solutions to combat the silent pandemic of AMR.