Homo-trimeric Structure of the Type IVb Minor Pilin CofB Suggests Mechanism of CFA/III Pilus Assembly in Human Enterotoxigenic Escherichia coli
Homo-trimeric Structure of the Type IVb Minor Pilin CofB Suggests Mechanism of CFA/III Pilus Assembly in Human Enterotoxigenic Escherichia coli
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DOI：
10.1016/j.jmb.2016.02.003
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发表时间：
2016-03-27
影响因子：
5.6
通讯作者：
Nakamura, Shota
中科院分区：
文献类型：
--
作者：
Kawahara, Kazuki;Oki, Hiroya;Nakamura, Shota
在革兰氏阴性菌中，IV型菌毛（T4 P）和II型分泌系统的进化相关的假菌毛的组装分别涉及称为菌毛蛋白和假菌毛蛋白的专门结构蛋白，并且被动态调节以促进细菌致病。以前的研究表明，一个结构的“尖端”样的杂合物形成通过至少三个次要的（假）菌毛蛋白的相互作用在这一过程中起着重要的作用，而一些成员的致病型IVb亚家族已知只有一个这样的次要菌毛蛋白亚基，其功能仍然是未知的。在这里，我们确定了晶体结构的IVb型小菌毛蛋白的定植因子抗原/III从人类肠上皮细胞大肠杆菌在1.88埃分辨率。的晶体结构，结合溶液中的物理化学分析，揭示了一个对称的同源三聚体的安排不同的杂复合物的未成年人（假）菌毛蛋白在其他T4 P和II型分泌系统。每一个BCLB单体采用独特的三结构域架构，其中C-末端富含β-折叠的凝集素结构域可以通过广泛的疏水相互作用有效地引发其菌毛蛋白样N-末端结构域的三聚体缔合，然后在中心铰链样结构域进行结构域交换。cofB的缺失产生细胞表面上没有可检测到的皮利形成的表型，而分子建模表明，特征性的同源三聚体结构的cofB是很好地位于由主要的菌毛蛋白cofA形成的定植因子抗原/III的菌毛尖端，这表明了次要的菌毛蛋白在T4 P组装的有效启动中的作用。(C)2016爱思唯尔有限公司版权所有。
In gram-negative bacteria, the assembly of type IV pilus (T4P) and the evolutionally related pseudopilus of type II secretion system involves specialized structural proteins called pilins and pseudopilins, respectively, and is dynamically regulated to promote bacterial pathogenesis. Previous studies have suggested that a structural "tip"-like hetero-complex formed through the interaction of at least three minor (pseudo) pilins plays an important role in this process, while some members of the pathogenic type IVb subfamily are known to have only one such minor pilin subunit whose function is still unknown. Here, we determined the crystal structure of the type IVb minor pilin CofB of colonization factor antigen/III from human enterotoxigenic Escherichia coli at 1.88-angstrom resolution. The crystal structure, in conjunction with physicochemical analysis in solution, reveals a symmetrical homo-trimeric arrangement distinct from the hetero-complexes of minor (pseudo) pilins observed in other T4P and type II secretion systems. Each CofB monomer adopts a unique three-domain architecture, in which the C-terminal beta-sheet-rich lectin domain can effectively initiate trimer association of its pilin-like N-terminal domain through extensive hydrophobic interactions followed by domain swapping at the central hinge-like domain. Deletion of cofB produces a phenotype with no detectable pili formation on the cell surface, while molecular modeling indicates that the characteristic homo-trimeric structure of CofB is well situated at the pilus tip of colonization factor antigen/III formed by the major pilin CofA, suggesting a role for the minor pilin in the efficient initiation of T4P assembly. (C) 2016 Elsevier Ltd. All rights reserved.