Structural and functional characterization of an essential RTX subdomain of Bordetella pertussis adenylate cyclase toxin
Structural and functional characterization of an essential RTX subdomain of Bordetella pertussis adenylate cyclase toxin
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DOI：
10.1074/jbc.m601594200
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发表时间：
2006-06-23
影响因子：
4.8
通讯作者：
Ladant, Daniel
中科院分区：
文献类型：
--
作者：
Bauche, Cecile;Chenal, Alexandre;Ladant, Daniel
腺苷酸环化酶毒素（CyaA）是百日咳的主要毒力因子之一。CyaA能够通过一种独特的机制侵入真核细胞，该机制包括CyaA催化结构域跨靶细胞质膜的钙依赖性直接易位。CyaA具有原型GGXG（N/D）DX（L/I/F）X（其中X代表任何氨基酸）的一系列富含甘氨酸和谷氨酸的九肽重复（残基1006-1613），其是细菌溶细胞素的RTX（毒素中的重复）家族的特征。这些重复序列以串联方式排列，并且可以折叠成特征性的平行β-螺旋或β-卷曲基序，其构成新型的钙结合结构，如铜绿假单胞菌碱性蛋白酶的三维结构所揭示的。在这里，我们的特点是从CyaA RTX亚结构域的各种片段的结构-功能关系。我们的研究结果表明，RTX功能单元包括串联重复的九肽基序和相邻的多肽片段，这是必不可少的折叠和钙的响应性的RTX模块。当钙离子与RTX重复序列结合时，相邻的非RTX序列的构象重排可以作为触发CyaA进入靶细胞的关键分子开关。
The adenylate cyclase toxin (CyaA) is one of the major virulence factors of Bordetella pertussis, the causative agent of whooping cough. CyaA is able to invade eukaryotic cells by a unique mechanism that consists in a calcium-dependent, direct translocation of the CyaA catalytic domain across the plasma membrane of the target cells. CyaA possesses a series of a glycine- and aspartate-rich nonapeptide repeats ( residues 1006-1613) of the prototype GGXG(N/D)DX(L/I/F)X ( where X represents any amino acid) that are characteristic of the RTX ( repeat in toxin) family of bacterial cytolysins. These repeats are arranged in a tandem fashion and may fold into a characteristic parallel beta-helix or beta-roll motif that constitutes a novel type of calcium binding structure, as revealed by the three-dimensional structure of the Pseudomonas aeruginosa alkaline protease. Here we have characterized the structure-function relationships of various fragments from the CyaA RTX subdomain. Our results indicate that the RTX functional unit includes both the tandem repeated nonapeptide motifs and the adjacent polypeptide segments, which are essential for the folding and calcium responsiveness of the RTX module. Upon calcium binding to the RTX repeats, a conformational rearrangement of the adjacent non-RTX sequences may act as a critical molecular switch to trigger the CyaA entry into target cells.