Adhesion is the initial step in the infection process of gram-negative bacteria. It is usually followed by the formation of biofilms that serve as a hub for further spread of the infection. Type V secretion systems engage in this process by binding to components of the extracellular matrix, which is the first step in the infection process. At the same time they provide protection from the immune system by either binding components of the innate immune system or by establishing a physical layer against aggressors. Trimeric autotransporter adhesins (TAAs) are of particular interest in this family of proteins as they possess a unique structural composition which arises from constraints during translocation. The sequence of individual domains can vary dramatically while the overall structure can be very similar to one another. This patchwork approach allows researchers to draw conclusions of the underlying function of a specific domain in a structure-based approach which underscores the importance of solving structures of yet uncharacterized TAAs and their individual domains to estimate the full extent of functions of the protein a priori. Here, we describe recent advances in understanding the translocation process of TAAs and give an overview of structural motifs that are unique to this class of proteins. The role of BpaC in the infection process of Burkholderia pseudomallei is highlighted as an exceptional example of a TAA being at the centre of infection initiation.

中文翻译：

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三聚体自转运蛋白粘附素的最新进展。


粘附是革兰氏阴性菌感染过程的第一步。随后通常会形成生物膜，作为感染进一步传播的中心。 V型分泌系统通过与细胞外基质的成分结合来参与这一过程，这是感染过程的第一步。同时，它们通过结合先天免疫系统的成分或建立针对侵略者的物理层来提供免受免疫系统侵害的保护。三聚体自转运蛋白粘附素 (TAA) 在该蛋白质家族中特别受关注，因为它们具有因易位过程中的限制而产生的独特结构组成。各个结构域的序列可能差异很大，而整体结构可能彼此非常相似。这种拼凑方法使研究人员能够在基于结构的方法中得出特定结构域的基本功能的结论，该方法强调了解决尚未表征的 TAA 及其各个结构域的结构以先验估计蛋白质功能的全部范围的重要性。在这里，我们描述了理解 TAA 易位过程的最新进展，并概述了此类蛋白质独特的结构基序。 BpaC 在类鼻疽伯克霍尔德氏菌感染过程中的作用被强调为 TAA 处于感染起始中心的一个特殊例子。