Thomassin Jenny-Lee, Santos Moreno Javier, Guilvout Ingrid, Tran Van Nhieu Guy, Francetic Olivera
Department of structural biology and chemistry, Biochemistry of Macromolecular Interactions Unit, Institut Pasteur, 28 rue du Dr Roux, 75724, Paris, Cedex 15, France.
Centre National de la Recherche Scientifique (CNRS), ERL6002, 75724, Paris, France.
Mol Microbiol. 2017 Jul;105(2):211-226. doi: 10.1111/mmi.13704. Epub 2017 May 18.
Nanomachines belonging to the type IV filament (Tff) superfamily serve a variety of cellular functions in prokaryotes, including motility, adhesion, electrical conductance, competence and secretion. The type 2 secretion system (T2SS) Tff member assembles a short filament called pseudopilus that promotes the secretion of folded proteins from the periplasm across the outer membrane of Gram-negative bacteria. A combination of structural, biochemical, imaging, computational and in vivo approaches had led to a working model for the assembled nanomachine. High-resolution cryo-electron microscopy and tomography provided the first view of several homologous Tff nanomachines in the cell envelope and revealed the structure of the outer membrane secretin channel, challenging current models of the overall stoichiometry of the T2SS. In addition, recent insights into exoprotein substrate features and interactions with the T2SS have led to new questions about the dynamics of the system and the role of the plasma membrane in substrate presentation. This micro-review will highlight recent advances in the field of type 2 secretion and discuss approaches that can be used to reach a mechanistic understanding of exoprotein recognition, integration into the machine and secretion.
属于IV型细丝（Tff）超家族的纳米机器在原核生物中发挥多种细胞功能，包括运动性、粘附、电导、感受态和分泌。2型分泌系统（T2SS）的Tff成员组装一种称为假菌毛的短细丝，促进折叠蛋白从周质穿过革兰氏阴性菌的外膜进行分泌。结构、生化、成像、计算和体内方法的结合产生了组装纳米机器的工作模型。高分辨率冷冻电子显微镜和断层扫描首次展示了细胞包膜中几种同源Tff纳米机器的情况，并揭示了外膜分泌素通道的结构，对当前T2SS整体化学计量模型提出了挑战。此外，最近对外蛋白底物特征及其与T2SS相互作用的深入了解引发了关于该系统动力学以及质膜在底物呈递中的作用的新问题。本微综述将重点介绍2型分泌领域的最新进展，并讨论可用于深入了解外蛋白识别、整合到机器中以及分泌机制的方法。
