Abstract

The chaperone-usher pathway of adhesive structures biogenesis is highly conserved in all Gram-negative bacteria. Pili are polymers of thousands protein subunits that possess conserved immunoglobuline-like structure denoted by lack of the seventh G strand. The effect of this structural defect is a hydrophobic acceptor cleft. The folding of protein subunits is strictly dependent on the action of specific periplasmic chaperone protein that complements the defective structure of a subunit by donating a specific donor strand. Stable chaperone-subunit complex migrates to the usher protein located in the outer membrane, where the process of protein subunits polymerization occurs. The crucial role in this mechanism is performed by chaperone the structure of which is highly conserved.The structural and functional conservation of this mechanism renders it a good potential target for development of a new class of antibacterial agents. Pilicides originally proposed by Svensson et al. in 2001 are a derivatives of a dihydrothiazolo ring-fused 2-pyridone scaffold that block formation of the adhesive organelles by impairing with the step of interaction between chaperone-subunit complex and usher protein. The anti-bacterial activity of pilicides as specific blockers of the chaperone-usher pathway has been confirmed only in the case of E. coli producing type 1 and P pili that represent the FGS type organelles. In our works we addressed a crucial question denoting spectrum of the anti-bacterial activity of pilicides: Are pilicides the potential anti-bacterial agents that target bacterial virulence in all pathogenic Gram-negative bacteria encoding chaperone-usher organelles of both FGL and FGS type? As a model of the FGL adhesive structures we used the uropathogenic E. coli strains producing Dr fimbriae. Biological evaluation based on the whole-cell assays showed that the E. coli Dr+ cultivated in the presence of pilicides possessed the amount of Dr fimbriae reduced to 85 %. This results in the high inhibition of bacteria adherence propensity to human cells. To prove that the observed inhibition of Dr fimbriae assembly is a consequence of pilicide impairing with the chaperone-usher pathway we measured the relative affinity of pilicides to the DraB protein using the surface plasmon resonance technique. Based on the conservation of the FGL type assembly machinery we conclude that the pilicides should be effective inhibitors of adhesive organelles biogenesis of this type.

Authors (6)