Chaperone-assisted assembly and molecular architecture of adhesive pili.
Chaperone-assisted assembly and molecular architecture of adhesive pili.
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DOI：
10.1146/annurev.mi.45.100191.002123
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发表时间：
1991
影响因子：
10.5
通讯作者：
S. Hultgren;Staff an Normark;S. Abraham
中科院分区：
文献类型：
--
作者：
S. Hultgren;Staff an Normark;S. Abraham
细菌菌毛的组装是一个复杂的过程，涉及结构蛋白和伴侣蛋白之间的特定分子相互作用。组装过程发生在分泌后，即亚基跨细胞质膜转运之后。在单个细胞中，数十万个相互作用的亚基通常被表面定位并组装成菌毛。周质伴侣通常需要与相互作用的亚基结合，并将它们分割成组装能力强的复合体。伴侣与亚基的结合显然保护了相互作用的表面，防止它们在细胞内错误的时间和地点聚集。菌毛很可能组装成线性聚合物，在通过特定的外膜通道转运后包装成右旋螺旋。每个菌毛细丝是结构亚基和包括粘附素部分在内的几个次要亚基的四元组装。虽然P和1型菌毛的组装和组织非常相似，但也有一些显著的差异。例如，P菌毛粘附素仅位于菌毛细丝的顶端，并形成形态上不同的结构的一部分。相反，I型菌毛的黏附部分间歇性地插入毛丝，但只有暴露在毛尖的粘附素分子才起作用。P菌毛之间同种受体识别的差异完全归因于各自粘附素分子的结构差异，而在1型菌毛中，结合特异性的差异归因于影响粘附素部分构象的菌毛细丝。对4型菌毛的结构或组装知之甚少，4型菌毛是由几种不同种类的革兰氏阴性细菌表达的一种独特的菌毛。淋病奈瑟菌的PILC装配基因在关闭状态时相变异，导致对细胞有毒害作用的未装配亚基的积累。这一过程对细胞施加了强大的选择压力，从而触发了菌毛结构基因的变化。因此，该生物体中菌毛的抗原变异可能在组装水平上受到调节。最后，分泌后组装中的周质伴侣的概念很可能是革兰氏阴性细菌生物学中的一种普遍现象。对菌毛组装的研究将继续提供有关大分子组装反应如何在细菌细胞中协调的细节，以及组装基因的调控如何深刻影响生物过程。
The assembly of bacterial pili as exemplified here by P and type 1 pili of E. coli is a complex process involving specific molecular interactions between structural and chaperone proteins. The assembly process occurs postsecretionally, i.e. after the subunits are translocated across the cytoplasmic membrane. In a single cell, hundreds of thousands of interactive subunits are typically surface localized and assembled into pili. Periplasmic chaperones are generally required to bind to the interactive subunits and partition them into assembly-competent complexes. The binding of the chaperone to the subunits apparently protects the interactive surfaces and prevents them from aggregating at the wrong time and place within the cell. Pili are most likely assembled into linear polymers that package into right-handed helices after their translocation through specific outer-membrane channels. Each pilus filament is a quaternary assembly of the structural subunit and several minor subunits including the adhesin moiety. Although the assembly and organization of P and type 1 pili are very similar, there are some notable differences. For example, the P pilus adhesin is located exclusively at the tips of the pilus filament and forms part of a morphologically distinct structure. In contrast, the adhesion moiety of type 1 pili is inserted into the pilus filament at intervals, but only the adhesin molecule exposed at the pilus tip is functional. The variability in isoreceptor recognition amongst P pili has been solely ascribed to structural differences in the respective adhesin molecules, whereas in type 1 pili, variability in binding specificity has been attributed to the pilus filament that influences the conformation of the adhesin moiety. Less is known about the structure or assembly of type 4 pili, which are a unique class of pili expressed by several different species of gram-negative bacteria. The phase variation of the pilC assembly gene in N. gonorrheae to the off state results in the accumulation of unassembled subunits toxic to the cells. This process exerts a strong selection pressure on the cells that triggers alterations in the pilin structural gene. Thus, antigenic variation of pili in this organism may be regulated at the level of assembly. Finally, the concept of periplasmic chaperones in postsecretional assembly is most likely a general phenomenon in the biology of gram-negative bacteria. The investigations of pilus assembly will continue to provide insight into the details of how macromolecular assembly reactions are coordinated in the bacterial cell and how the regulation of assembly genes can profoundly affect biological processes.