Extraintestinal pathogenic Escherichia coli utilizes the surface-expressed elongation factor Tu to bind and acquire iron from holo-transferrin

ABSTRACT

Extraintestinal pathogenic Escherichia coli (ExPEC) is a common anthropozoonotic pathogen that causes systemic infections. To establish infection, ExPEC must utilize essential nutrients including iron from the host. Transferrin is an important iron source for multiple bacteria. However, the mechanism by which ExPEC utilizes transferrin remains unclear. In this study, we found that iron-saturated holo-transferrin rather than iron-free apo-transferrin promoted the vitality of ExPEC in heat-inactivated human serum. The multifunctional protein Elongation factor Tu (EFTu) worked as a holo-transferrin binding protein. EFTu not only bound holo-transferrin rather than apo-transferrin but also released transferrin-related iron, with all domains of EFTu involved in holo-transferrin binding and iron release events. We also identified the surface location of EFTu on ExPEC. Overexpression of EFTu on the surface of nonpathogenic E. coli not only promoted the binding of bacteria to holo-transferrin but also facilitated the uptake of transferrin-related iron. More importantly, it significantly enhanced the survival of E. coli in heat-inactivated human serum, which was positively correlated with holo-transferrin but not apo-transferrin. Our research revealed a novel function of EFTu in binding holo-transferrin to promote iron uptake by bacteria, suggesting that EFTu was a potential virulence factor of ExPEC. In addition, our study provided research avenues into the iron acquisition and pathogenicity mechanisms of ExPEC.

KEYWORDS:

• Extraintestinal pathogenic Escherichia coli
• elongation factor Tu
• holo-transferrin
• transferrin-binding protein
• serum resistance

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [31872479 and 32172858] and the Priority Academic Program Development of Jiangsu Higher Education Institutions fund (PAPD).