The usher N terminus is the initial targeting site for chaperone-subunit complexes and participates in subsequent pilus biogenesis events
The usher N terminus is the initial targeting site for chaperone-subunit complexes and participates in subsequent pilus biogenesis events
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DOI：
10.1128/jb.186.16.5321-5331.2004
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发表时间：
2004-08-01
影响因子：
3.2
通讯作者：
Thanassi, DG
中科院分区：
文献类型：
--
作者：
Ng, TW;Akman, L;Thanassi, DG
泌尿道致病性大肠杆菌表面的菌毛生物发生需要伴侣/引座途径，这是一般分泌途径的末端分支。在此途径中，周质伴侣-亚基复合物靶向外膜（OM）引座，将亚基组装成菌毛并分泌到细胞表面。 OM 中蛋白质分泌的分子机制尚不清楚。对 P 菌毛引座 PapC 和 1 型菌毛引座 FimD 进行诱变，以阐明 OM 菌毛生物发生的初始阶段。成熟 PapC N 末端残基 2 至 11 的删除消除了分子伴侣亚基复合物对引导者的靶向作用，并使 PapC 对于菌毛生物发生失去功能。类似地，分子伴侣亚基结合和菌毛生物发生需要完整的 FimD N 末端。对 PapC-FimD 嵌合体和 PapC N 端片段的分析将伴侣亚基靶向结构域定位于 PapC 的前 124 个残基。在该结构域中进行单个丙氨酸取代突变，阻断菌毛生物发生，但不影响分子伴侣-亚基复合物的靶向。因此，引座子 N 末端不仅仅充当伴侣-亚基复合物的静态结合位点，而且还参与随后的菌毛组装事件。
Pilus biogenesis on the surface of uropathogenic Escherichia coli requires the chaperone/usher pathway, a terminal branch of the general secretory pathway. In this pathway, periplasmic chaperone-subunit complexes target an outer membrane (OM) usher for subunit assembly into pili and secretion to the cell surface. The molecular mechanisms of protein secretion across the OM are not well understood. Mutagenesis of the P pilus usher PapC and the type 1 pilus usher FimD was undertaken to elucidate the initial stages of pilus biogenesis at the OM. Deletion of residues 2 to 11 of the mature PapC N terminus abolished the targeting of the usher by chaperone-subunit complexes and rendered PapC nonfunctional for pilus biogenesis. Similarly, an intact FimD N terminus was required for chaperone-subunit binding and pilus biogenesis. Analysis of PapC-FimD chimeras and N-terminal fragments of PapC localized the chaperone-subunit targeting domain to the first 124 residues of PapC. Single alanine substitution mutations were made in this domain that blocked pilus biogenesis but did not affect targeting of chaperone-subunit complexes. Thus, the usher N terminus does not function simply as a static binding site for chaperone-subunit complexes but also participates in subsequent pilus assembly events.