Université Grenoble Alpes, CNRS, CEA, IBS, Grenoble, France.
J Virol. 2023 Mar 30;97(3):e0158422. doi: 10.1128/jvi.01584-22. Epub 2023 Feb 13.
Bacteriophages, viruses infecting bacteria, recognize their host with high specificity, binding to either saccharide motifs or proteins of the cell wall of their host. In the majority of bacteriophages, this host recognition is performed by receptor binding proteins (RBPs) located at the extremity of a tail. Interaction between the RBPs and the host is the trigger for bacteriophage infection, but the molecular details of the mechanisms are unknown for most bacteriophages. Here, we present the electron cryomicroscopy (cryo-EM) structure of bacteriophage T5 RBP in complex with its Escherichia coli receptor, the iron ferrichrome transporter FhuA. Monomeric RBP is located at the extremity of T5's long flexible tail, and its irreversible binding to FhuA commits T5 to infection. Analysis of the structure of RBP within the complex, comparison with its AlphaFold2-predicted structure, and its fit into a previously determined map of the T5 tail tip in complex with FhuA allow us to propose a mechanism of transmission of the RBP receptor binding to the straight fiber, initiating the cascade of events that commits T5 to DNA ejection. Tailed bacteriophages specifically recognize their bacterial host by interaction of their receptor binding protein(s) (RBPs) with saccharides and/or proteins located at the surface of their prey. This crucial interaction commits the virus to infection, but the molecular details of this mechanism are unknown for the majority of bacteriophages. We determined the structure of bacteriophage T5 RBP in complex with its E. coli receptor, FhuA, by cryo-EM. This first structure of an RBP bound to its protein receptor allowed us to propose a mechanism of transmission of host recognition to the rest of the phage, ultimately opening the capsid and perforating the cell wall and, thus, allowing safe channeling of the DNA into the host cytoplasm.
噬菌体是感染细菌的病毒，它们具有高度特异性识别宿主的能力，通过与宿主细胞壁上的糖基或蛋白结合来识别宿主。在大多数噬菌体中，这种宿主识别是由位于尾部末端的受体结合蛋白（RBP）完成的。RBP 与宿主的相互作用是噬菌体感染的触发因素，但对于大多数噬菌体，其机制的分子细节尚不清楚。在这里，我们展示了噬菌体 T5 RBP 与其大肠杆菌受体铁载体 FhuA 复合物的电子 cryo-EM 结构。单体 RBP 位于 T5 长而灵活的尾部末端，它与 FhuA 的不可逆结合使 T5 能够感染。对复合物中 RBP 结构的分析、与 AlphaFold2 预测结构的比较，以及其与之前确定的 T5 尾部末端与 FhuA 复合物的结构拟合，使我们能够提出 RBP 受体结合向直纤维传递的机制，从而引发使 T5 能够将 DNA 喷射出去的一系列事件。有尾噬菌体通过其受体结合蛋白（RBP）与位于猎物表面的糖基和/或蛋白相互作用，特异性识别其细菌宿主。这种关键的相互作用使病毒能够感染，但对于大多数噬菌体来说，这种机制的分子细节尚不清楚。我们通过 cryo-EM 确定了噬菌体 T5 RBP 与其大肠杆菌受体 FhuA 的复合物结构。第一个与蛋白受体结合的 RBP 结构使我们能够提出一种将宿主识别传递给噬菌体其余部分的机制，最终打开衣壳并穿透细胞壁，从而允许 DNA 安全地进入宿主细胞质。
