MOE Joint International Research Laboratory of Animal Health and Food Safety, Key Lab of Animal Bacteriology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China.
School of Life Science and Technology, China Pharmaceutical University, Nanjing, China.
Virulence. 2022 Dec;13(1):698-713. doi: 10.1080/21505594.2022.2066274.
Extraintestinal pathogenic (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 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 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.
肠外致病性菌（ExPEC）是一种常见的人畜共患病原体，可引起全身感染。为了建立感染，ExPEC 必须利用包括来自宿主的铁在内的必需营养素。转铁蛋白是多种细菌的重要铁源。然而，ExPEC 利用转铁蛋白的机制尚不清楚。在这项研究中，我们发现饱和的铁结合态转铁蛋白而非无铁的脱铁转铁蛋白促进了热失活人血清中 ExPEC 的活力。多功能蛋白延伸因子 Tu（EFTu）是一种铁结合态转铁蛋白结合蛋白。EFTu 不仅结合铁结合态转铁蛋白而非脱铁转铁蛋白，还释放与转铁蛋白相关的铁，EFTu 的所有结构域都参与铁结合和释放事件。我们还确定了 EFTu 在 ExPEC 上的表面位置。非致病性菌表面过表达 EFTu 不仅促进了细菌与铁结合态转铁蛋白的结合，还促进了转铁蛋白相关铁的摄取。更重要的是，它显著增强了在热失活人血清中存活的能力，这与铁结合态转铁蛋白呈正相关，而与脱铁转铁蛋白无关。我们的研究揭示了 EFTu 在结合铁结合态转铁蛋白以促进细菌摄取铁方面的新功能，表明 EFTu 是 ExPEC 的潜在毒力因子。此外，我们的研究为 ExPEC 的铁摄取和致病性机制提供了研究途径。
