Physical properties of the specific PapG–galabiose binding in E. coli P pili-mediated adhesion

Abstract

Detailed analyses of the mechanisms that mediate binding of the uropathogenic Escherichia coli to host cells are essential, as attachment is a prerequisite for the subsequent infection process. We explore, by means of force measuring optical tweezers, the interaction between the galabiose receptor and the adhesin PapG expressed by P pili on single bacterial cells. Two variants of dynamic force spectroscopy were applied based on constant and non-linear loading force. The specific PapG-galabiose binding showed typical slip-bond behaviour in the force interval (30-100 pN) set by the pilus intrinsic biomechanical properties. Moreover, it was found that the bond has a thermodynamic off-rate and a bond length of 2.6 x 10(-3) s(-1) and 5.0 A, respectively. Consequently, the PapG-galabiose complex is significantly stronger than the internal bonds in the P pilus structure that stabilizes the helical chain-like macromolecule. This finding suggests that the specific binding is strong enough to enable the P pili rod to unfold when subjected to strong shear forces in the urinary tract. The unfolding process of the P pili rod promotes the formation of strong multipili interaction, which is important for the bacterium to maintain attachment to the host cells.

Dynamic Modulation of Fimbrial Extension and FimH-Mannose Binding Force on Live Bacteria Under pH Changes: A Molecular Atomic Force Microscopy Analysis

“…These observations underpin some flexibility of type 1 fimbriae structures, probably depending on their physiological state, in line with previous conclusions. 5,[16][17][18] Impact of pH and pulling rate on FimH-mannose interaction.…”

“…It was reported that both pili are highly flexible and they may be viewed as dynamic structures with spring-like properties. 5,[16][17][18] Indeed, when bacteria were subjected to hydrodynamic constrains, these structures maintain bacterial attachment to host cells or surfaces by reducing the impact of flushes and associated mechanical stress 5,19 following an unwinding of the pointed out that the length of P-pili and type 1 fimbriae could increase by a factor 5 following such unwinding process under high shear stress conditions. [20][21][22] The forced unraveling of type 1 fimbriae is reversible, with helical rewinding taking place for shear forces of magnitude ~ 60 pN.…”

Characterization of the Biomechanical Properties of T4 Pili Expressed by Streptococcus pneumoniae—A Comparison between Helix‐like and Open Coil‐like Pili

“…The pilus was exposed to further discontinuities at forces outside the range of the plot, why the retraction curve appears shifted from the elongation curve. Dashed curves: fits of Equation (1) As was alluded to above, the persistence length of T4 pili was assessed to 2.1 AE1.7 nm, which is similar to the length of a RrgB subunit, but slightly shorter than those of P and type 1 pili previously found to be 3.3 AE 0.6 nm [21] and 3.3 AE 1.6 nm, [17] respectively. This suggests that T4 pili have a structure that is significantly more flexible than closed helix-like pili, and similar to, or slightly more flexible than, open helix-like pili, expressed by UPEC.…”

Reprint of “Biogenesis and adhesion of type 1 and P pili”

“…The adhesins do appear to be adapted to their particular environment; FimH has a 'catch bond' which allows the adhered bacteria to withstand the high pressure urine flows of the bladder, whereas the P pilus has a 'slip bond', suitable for the more regular flows of the kidneys, which allows for maximum dissemination of bacteria [63][64][65].…”