Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, Japan.
Appl Environ Microbiol. 2021 Jun 11;87(13):e0042321. doi: 10.1128/AEM.00423-21.
Bacteriophages are the most abundant and diverse biological entities on Earth. Phages exhibit strict host specificity that is largely conferred by adsorption. However, the mechanism underlying this phage host specificity remains poorly understood. In this study, we examined the interaction between outer membrane protein C (OmpC), one of the Escherichia coli receptors, and the long tail fibers of bacteriophage T4. T4 phage uses OmpC of the K-12 strain, but not of the O157 strain, for adsorption, even though OmpCs from the two E. coli strains share 94% homology. We identified amino acids P177 and F182 in loop 4 of the K-12 OmpC as essential for T4 phage adsorption in the copresence of loops 1 and 5. Analyses of phage mutants capable of adsorbing to OmpC mutants demonstrated that amino acids at positions 937 and 942 of the gp37 protein, which is present in the distal tip (DT) region of the T4 long tail fibers, play an important role in adsorption. Furthermore, we created a T4 phage mutant library with artificial modifications in the DT region and isolated and characterized multiple phage mutants capable of adsorbing to OmpC of the O157 strain or lipopolysaccharide of the K-12 strain. These results shed light on the mechanism underlying the phage host specificity mediated by gp37 and OmpC and may be useful in the development of phage therapy via artificial modifications of the DT region of T4 phage. Understanding the host specificity of phages will lead to the development of phage therapy. The interaction between outer membrane protein C (OmpC), one of the Escherichia coli receptors, and the gp37 protein present in the distal tip (DT) region of the long tail fibers of T4 bacteriophages largely determines their host specificity. Here, we elucidated the amino acid residues important for the interaction between gp37 and OmpC. This result suggests that the shapes of both proteins at the binding interface play important roles in their interactions, which are likely mediated by multiple residues of both binding partners. Additionally, we successfully isolated multiple phage mutants capable of adsorbing to a variety of E. coli receptors using a mutant T4 phage library with artificial modifications in the DT region, providing a foundation for the alteration of the host specificity.
噬菌体是地球上最丰富和最多样化的生物实体。噬菌体表现出严格的宿主特异性，这种特异性主要是通过吸附来赋予的。然而，这种噬菌体宿主特异性的机制仍然知之甚少。在这项研究中，我们研究了大肠杆菌受体之一的外膜蛋白 C（OmpC）与 T4 噬菌体的长尾纤维之间的相互作用。T4 噬菌体使用 K-12 株的 OmpC，而不是 O157 株的 OmpC 进行吸附，尽管来自两种大肠杆菌株的 OmpC 具有 94%的同源性。我们确定了 K-12 OmpC 环 4 中的氨基酸 P177 和 F182 对于在环 1 和 5 共存在的情况下 T4 噬菌体的吸附是必需的。对能够吸附到 OmpC 突变体的噬菌体突变体的分析表明，gp37 蛋白上位于长尾纤维远端尖端（DT）区域的位置 937 和 942 的氨基酸在吸附中起重要作用。此外，我们创建了一个在 DT 区域进行人工修饰的 T4 噬菌体突变体文库，并分离和鉴定了多个能够吸附到 O157 株 OmpC 或 K-12 株脂多糖的噬菌体突变体。这些结果阐明了由 gp37 和 OmpC 介导的噬菌体宿主特异性的机制，并可能有助于通过人工修饰 T4 噬菌体的 DT 区域来开发噬菌体治疗。了解噬菌体的宿主特异性将导致噬菌体治疗的发展。大肠杆菌受体之一的外膜蛋白 C（OmpC）与 T4 噬菌体长尾纤维的远端尖端（DT）区域中存在的 gp37 蛋白之间的相互作用在很大程度上决定了它们的宿主特异性。在这里，我们阐明了 gp37 和 OmpC 之间相互作用的重要氨基酸残基。这一结果表明，在结合界面上的两种蛋白质的形状在它们的相互作用中起着重要作用，这可能是由两个结合伙伴的多个残基介导的。此外，我们使用在 DT 区域进行人工修饰的突变 T4 噬菌体文库成功分离了多个能够吸附多种大肠杆菌受体的噬菌体突变体，为改变宿主特异性提供了基础。
