Structural Basis of Chaperone Recognition of Type III Secretion System Minor Translocator Proteins
Structural Basis of Chaperone Recognition of Type III Secretion System Minor Translocator Proteins
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DOI：
10.1074/jbc.m110.111278
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发表时间：
2010-07-23
影响因子：
4.8
通讯作者：
Dessen, Andrea
中科院分区：
文献类型：
--
作者：
Job, Viviana;Mattei, Pierre-Jean;Dessen, Andrea
III型分泌系统（T3 SS）是许多革兰氏阴性病原体（包括医院病原体铜绿假单胞菌）采用的复杂纳米机器，用于将毒素直接注入真核细胞的细胞质中。所有T3 SS的一个关键组成部分是易位子，一种插入靶细胞膜的蛋白质通道，允许毒素进入靶细胞。在大多数细菌物种中，两种不同的膜蛋白（“易位子”）参与易位子的形成，然而，在细菌细胞质中，它们仍然与共同的伴侣蛋白相关。到目前为止，一个伴侣分子识别两个不同的易位蛋白的策略是未知的。在这里，我们报告的晶体结构之间的复合物的假单胞菌易位分子伴侣PcrH和一个短的区域从未成年人易位PopD。PcrH显示一个7-螺旋tetratricopeptide重复折叠，在其凹区内含有PopD肽，最初认为参与识别主要的转运蛋白PopB。点突变引入到PcrH相互作用区域的PopD阻碍转运蛋白伴侣识别在体外，并导致减值的细菌细胞毒性对巨噬细胞在体内。这些结果表明T3 SS转运蛋白伴侣与其伴侣分子形成二元复合物，并且必须严格维持其相互作用区域的稳定性以保证细菌的感染性。PcrH-PopD复合物在许多致病菌株中显示同源物，并且可以代表抗生素开发的新的潜在靶标。
The type III secretion system (T3SS) is a complex nanomachine employed by many Gram-negative pathogens, including the nosocomial agent Pseudomonas aeruginosa, to inject toxins directly into the cytoplasm of eukaryotic cells. A key component of all T3SS is the translocon, a proteinaceous channel that is inserted into the target membrane, which allows passage of toxins into target cells. In most bacterial species, two distinct membrane proteins (the "translocators") are involved in translocon formation, whereas in the bacterial cytoplasm, however, they remain associated to a common chaperone. To date, the strategy employed by a single chaperone to recognize two distinct translocators is unknown. Here, we report the crystal structure of a complex between the Pseudomonas translocator chaperone PcrH and a short region from the minor translocator PopD. PcrH displays a 7-helical tetratricopeptide repeat fold that harbors the PopD peptide within its concave region, originally believed to be involved in recognition of the major translocator, PopB. Point mutations introduced into the PcrH-interacting region of PopD impede translocator-chaperone recognition in vitro and lead to impairment of bacterial cytotoxicity toward macrophages in vivo. These results indicate that T3SS translocator chaperones form binary complexes with their partner molecules, and the stability of their interaction regions must be strictly maintained to guarantee bacterial infectivity. The PcrH-PopD complex displays homologs among a number of pathogenic strains and could represent a novel, potential target for antibiotic development.