CEA, Institut de Biologie Structurale Jean-Pierre Ebel, Grenoble, France.
Biochimie. 2012 Sep;94(9):1982-9. doi: 10.1016/j.biochi.2012.05.021. Epub 2012 May 29.
The majority of bacterial viruses are bacteriophages bearing a tail that serves to recognise the bacterial surface and deliver the genome into the host cell. Infection is initiated by the irreversible interaction between the viral receptor binding protein (RBP) and a receptor at the surface of the bacterium. This interaction results ultimately in the phage DNA release in the host cytoplasm. Phage T5 infects Escherichia coli after binding of its RBP pb5 to the outer membrane ferrichrome transporter FhuA. Here, we have studied the complex formed by pb5 and FhuA by a variety of biophysical and biochemical techniques. We show that unlike RBPs of known structures, pb5 probably folds as a unique domain fulfilling both functions of binding to the host receptor and interaction with the rest of the phage. Pb5 likely binds to the domain occluding the β-barrel of FhuA as well as to external loops of the barrel. Furthermore, upon binding to FhuA, pb5 undergoes conformational changes, at the secondary and tertiary structure level that would be the key to the transmission of the signal through the tail to the capsid, triggering DNA release. This is the first structural information regarding the binding of a RBP to a proteic receptor.
大多数细菌病毒是带有尾巴的噬菌体，尾巴用于识别细菌表面并将基因组递送到宿主细胞中。感染是由病毒受体结合蛋白 (RBP) 与细菌表面受体之间的不可逆相互作用引发的。这种相互作用最终导致噬菌体 DNA 在宿主细胞质中释放。噬菌体 T5 在其 RBP pb5 与外膜 ferrichrome 转运蛋白 FhuA 结合后感染大肠杆菌。在这里，我们使用各种生物物理和生化技术研究了由 pb5 和 FhuA 形成的复合物。我们表明，与已知结构的 RBP 不同，pb5 可能折叠为一个独特的结构域，同时履行与宿主受体结合和与噬菌体其余部分相互作用的两种功能。pb5 可能与 occluding FhuA 的 β-桶的结构域以及桶的外部环结合。此外，pb5 在与 FhuA 结合后，在二级和三级结构水平上发生构象变化，这将是通过尾巴将信号传递到衣壳并触发 DNA 释放的关键。这是关于 RBP 与蛋白受体结合的第一个结构信息。
