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首页> 外文期刊>Journal of Molecular Biology >Chaperone-independent Folding of Type 1 Pilus Domains.
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Chaperone-independent Folding of Type 1 Pilus Domains.

机译：类型1 Pilus域的伴侣独立折叠。

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摘要

An elementary step in the assembly of adhesive type 1 pili of Escherichia coli is the folding of structural pilus subunits in the periplasm. The previously determined X-ray structure of the complex between the type 1 pilus adhesin FimH and the periplasmic pilus assembly chaperone FimC has shown that FimH consists of a N-terminal lectin domain and a C-terminal pilin domain, and that FimC exclusively interacts with the pilin domain. The pilin domain fold, which is common to all pilus subunits, is characterized by an incomplete beta-sheet that is completed by a donor strand from FimC in the FimC-FimH complex. This, together with unsuccessful attempts to refold isolated, urea-denatured FimH in vitro had suggested that folding of pilin domains strictly depends on sequence information provided by FimC. We have now analyzed in detail the folding of FimH and its two isolated domains in vitro. We find that not only the lectin domain, but also the pilin domain can fold autonomously and independently of FimC. However, the thermodynamic stability of the pilin domain is very low (8-10kJmol(-1)) so that a significant fraction of the domain is unfolded even in the absence of denaturant. This explains the high tendency of structural pilus subunits to aggregate non-specifically in the absence of stoichiometric amounts of FimC. Thus, pilus chaperones prevent non-specific aggregation of pilus subunits by native state stabilization after subunit folding.
机译：组装大肠杆菌粘附性1型菌毛的一个基本步骤是在周质中折叠结构菌毛亚基。先前确定的1型菌毛粘附素FimH与周质菌毛组装伴侣FimC之间的复合物的X射线结构表明，FimH由N端凝集素结构域和C端菌毛结构域组成，并且FimC仅与pilin域。所有菌毛亚基共有的菌毛蛋白结构域折叠的特征是不完整的β-折叠，该折叠由FimC-FimH复合物中来自FimC的供体链完成。这与在体外重新折叠分离的，尿素变性的FimH的失败尝试一起表明，菌毛蛋白结构域的折叠严格取决于FimC提供的序列信息。现在，我们已经详细分析了FimH及其两个孤立域的折叠。我们发现，不仅凝集素结构域，而且菌毛素结构域也可以独立于FimC自主折叠。但是，菌毛蛋白结构域的热力学稳定性非常低（8-10kJmol（-1）），因此即使没有变性剂，该结构域的大部分也不会展开。这解释了在没有化学计量的FimC的情况下，结构菌毛亚基高度非特异性聚集的趋势。因此，菌毛伴侣可以通过亚基折叠后的天然状态稳定来防止菌毛亚基的非特异性聚集。

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