The Outer Membrane Usher Guarantees the Formation of Functional Pili by Selectively Catalyzing Donor-Strand Exchange between Subunits That Are Adjacent in the Mature Pilus
The Outer Membrane Usher Guarantees the Formation of Functional Pili by Selectively Catalyzing Donor-Strand Exchange between Subunits That Are Adjacent in the Mature Pilus
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DOI：
10.1016/j.jmb.2009.12.005
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发表时间：
2010-02-12
影响因子：
5.6
通讯作者：
Glockshuber, Rudi
中科院分区：
文献类型：
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作者：
Nishiyama, Mireille;Glockshuber, Rudi
尿路致病性大肠杆菌的1型皮利是由保守的伴侣/引导途径组装和分泌的粘附表面细胞器的原型。它们由四种不同的同源蛋白质亚基组成，需要以确定的顺序组装。在周质中，菌毛分子伴侣FimC向亚基提供β链片段以完成其不完善的免疫球蛋白样折叠。在亚基组装过程中，分子伴侣的这一部分在称为供体链交换的反应中被进入亚基的氨基末端延伸取代。迄今为止，协调亚基组装的分子机制，特别是外膜引导FimD的作用，仍然知之甚少。我们发现FimC和不同菌毛亚基之间的复合物与FimD的氨基末端底物识别结构域的结合是一个非常快的过程，在20 ℃时结合速率常数在10（7）-10（8）M-1 s（-1）范围内。此外，我们证明，菌毛亚基的有序组装是一个后果的引座员的能力，选择性地催化组装的定义亚基亚基对是相邻的成熟菌毛。因此，引导员在亚基对之间的供体链交换阶段协调菌毛亚基的组装，而不是在伴侣亚基复合物的初始结合水平。(C)2009爱思唯尔有限公司保留所有权利。
Type 1 pili from uropathogenic Escherichia coli are a prototype of adhesive surface organelles assembled and secreted by the conserved chaperone/usher pathway. They are composed of four different homologous protein subunits that need to be assembled in a defined order. In the periplasm, the pilus chaperone FimC donates a beta-strand segment to the subunits to complete their imperfect immunoglobulin-like fold. During subunit assembly, this segment of the chaperone is displaced by an amino-terminal extension of an incoming subunit in a reaction termed donor-strand exchange. To date, the molecular mechanisms underlying the coordinated subunit assembly, in particular the role of the outer membrane usher FimD, are still poorly understood. Here we show that the binding of complexes between FimC and the different pilus subunits to the amino-terminal substrate recognition domain of FimD is an extremely fast process, with association rate constants in the range of 10(7)-10(8) M-1 s(-1) at 20 degrees C. Furthermore, we demonstrate that the ordered assembly of pilus subunits is a consequence of the usher's ability to selectively catalyze the assembly of defined subunit-subunit pairs that are adjacent in the mature pilus. The usher therefore coordinates the assembly of pilus subunits at the stage of donor-strand exchange between pairs of subunits and not at the level of the initial binding of chaperone-subunit complexes. (C) 2009 Elsevier Ltd. All rights reserved.