VirB11 as molecular target for the development of bacterial conjugation inhibitors

Abstract

Bacterial conjugation constitutes the main mechanism for the dissemination of antibiotic resistance genes. Therefore, the search for specific conjugation inhibitors is crucial in the fight against multi-resistant pathogens. Several compounds have been proposed to be able to inhibit conjugation (Michel-Briand and Laporte, 1985; Hooper et al., 1989; Conter et al., 2002; Leite et al., 2005; Lujan et al., 2007). However, unsaturated fatty acids (uFAs) and 2-alkynoic fatty acids (2-aFAs) are the only specific conjugation inhibitors found so far (Fernández-Lopez et al., 2005; Getino et al., 2015). We have found that TrwD, the VirB11 homolog in the conjugative R388 plasmid, is the specific target of these inhibitors (Ripoll-Rozada et al., 2016). Characterization of the kinetic parameters and molecular docking simulations have let us to suggest a model for inhibition. VirB11 proteins belong to the super-family of secretion AAA+ traffic ATPases, which includes members of Type II secretion system, Type IV pilus biogenesis and arch aeal flagellar assembly machineries (Planet et al., 2001). Members of this family are characterized by a common architecture consisting of hexameric rings in which each monomer is formed by two domains connected by a flexible linker of a variable length (Planet et al., 2001; Hare et al., 2006; Peña and Arechaga, 2013). In a previous work, we described the catalytic mechanism of ATP hydrolysis by VirB11 protein (Ripoll-Rozada et al., 2012). Interestingly, we have found that the mode of action of the uFAs is by binding to a pocket formed by the N-terminal domain (NTD) and the linker, preventing the pivoting movement of the NTD over the catalytic C-terminal domain (CTD). These results do not only contribute to a better understanding of the VirB11 proteins but also lie the foundations for the development of new and more effectiv e drugs to control bacterial conjugation.