Combination of Two Separate Binding Domains Defines Stoichiometry between Type III Secretion System Chaperone IpgC and Translocator Protein IpaB
Combination of Two Separate Binding Domains Defines Stoichiometry between Type III Secretion System Chaperone IpgC and Translocator Protein IpaB
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DOI：
10.1074/jbc.m110.135616
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发表时间：
2010-12-17
影响因子：
4.8
通讯作者：
Kolbe, Michael
中科院分区：
文献类型：
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作者：
Lokareddy, Ravi Kumar;Lunelli, Michele;Kolbe, Michael
肠道致病菌利用的 III 型分泌系统 (TTSS) 需要存在小的、酸性毒力相关的伴侣才能有效感染宿主细胞。我们采用生化和细胞技术相结合来定义易位子 IpaB 和 IpaC 中与福氏志贺氏菌伴侣 IpgC 相关的伴侣结合域 (CBD)。我们在 IpaB 中发现了一种新的 CBD，并进一步精确地绘制了两种易位蛋白中 CBD 的边界。在 IpaC 中，单个结合域与 IpgC 关联。在 IpaB 中，我们表明新表征的 CBD 的结合对于维持伴侣-易位子复合物的三元排列至关重要。这种迄今为止未知的功能也反映在共晶结构中，其中 IpgC 二聚体与包含两个 CBD 的 IpaB 片段结合。此外，在缺乏这种新型 CBD 的情况下，IpaB/IpgC 复合物会聚集。伴侣蛋白对蛋白质结构域的双重识别促进了正确的伴侣-底物组织，描述了 TTSS 相关伴侣-底物复合物的新功能。
Type III secretion systems (TTSSs) utilized by enteropathogenic bacteria require the presence of small, acidic virulence-associated chaperones for effective host cell infection. We adopted a combination of biochemical and cellular techniques to define the chaperone binding domains (CBDs) in the translocators IpaB and IpaC associated with the chaperone IpgC from Shigella flexneri. We identified a novel CBD in IpaB and furthermore precisely mapped the boundaries of the CBDs in both translocator proteins. In IpaC a single binding domain associates with IpgC. In IpaB, we show that the binding of the newly characterized CBD is essential in maintaining the ternary arrangement of chaperone-translocator complex. This hitherto unknown function is reflected in the co-crystal structure as well, with an IpgC dimer bound to an IpaB fragment comprising both CBDs. Moreover, in the absence of this novel CBD the IpaB/IpgC complex aggregates. This dual-recognition of a domain in the protein by the chaperone in facilitating the correct chaperone-substrate organization describes a new function for the TTSS associated chaperone-substrate complexes.