Pertactin β-helix folding mechanism suggests common themes for the secretion and folding of autotransporter proteins
Pertactin β-helix folding mechanism suggests common themes for the secretion and folding of autotransporter proteins
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DOI：
10.1073/pnas.0507923103
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发表时间：
2006-03-28
影响因子：
11.1
通讯作者：
Clark, PL
中科院分区：
文献类型：
--
作者：
Junker, M;Schuster, CC;Clark, PL
革兰氏阴性菌分泌的许多毒力因子是自转运蛋白。自转运蛋白分泌的最后一步是由共翻译的C-末端孔蛋白结构域介导的乘客结构域的C -> N-末端穿过外膜（OM）。天然结构仅在最后的分泌步骤后形成，这既不需要ATP也不需要质子梯度。序列分析显示，尽管自转运蛋白乘客结构域之间的大小、序列和功能多样性，但预测> 97%形成平行β-螺旋，表明这种结构拓扑结构可能对分泌很重要。我们报告的折叠行为的percovern，一个自转运乘客域从百日咳杆菌。percusn β-螺旋在孤立状态下可逆地折叠，但折叠比基于大小和天然状态拓扑结构的预期慢得多。令人惊讶的是，在折叠过程中，尽管折叠非常缓慢，但percavin不容易聚集。有趣的是，平衡变性导致部分折叠结构的形成，这是一个稳定的核心，包含蛋白质的C-末端一半。检查的percubin晶体结构没有发现任何明显的原因，增强稳定性的C端。在体内，在OM分泌之前，缓慢折叠将防止乘客结构域在周质中过早折叠。此外，额外的稳定性的C-末端梯级的p-螺旋可能作为一个模板，在OM分泌过程中形成的天然蛋白质，因此，矢量折叠的β-螺旋可能有助于能量无关的易位机制。再加上序列分析，这里提出的结果表明，一般的机制，自我转运分泌。
Many virulence factors secreted from pathogenic Gram-negative bacteria are autotransporter proteins. The final step of autotransporter secretion is C -> N-terminal threading of the passenger domain through the outer membrane (OM), mediated by a co-translated C-terminal porin domain. The native structure is formed only after this final secretion step, which requires neither ATP nor a proton gradient. Sequence analysis reveals that, despite size, sequence, and functional diversity among autotransporter passenger domains, > 97% are predicted to form parallel beta-helices, indicating this structural topology may be important for secretion. We report the folding behavior of pertactin, an autotransporter passenger domain from Bordetella pertussis. The pertactin beta-helix folds reversibly in isolation, but folding is much slower than expected based on size and native-state topology. Surprisingly, pertactin is not prone to aggregation during folding, even though folding is extremely slow. Interestingly, equilibrium denaturation results in the formation of a partially folded structure, a stable core comprising the C-terminal half of the protein. Examination of the pertactin crystal structure does not reveal any obvious reason for the enhanced stability of the C terminus. in vivo, slow folding would prevent premature folding of the passenger domain in the periplasm, before OM secretion. Moreover, the extra stability of the C-terminal rungs of the p-helix might serve as a template for the formation of native protein during OM secretion; hence, vectorial folding of the beta-helix could contribute to the energy-independent translocation mechanism. Coupled with the sequence analysis, the results presented here suggest a general mechanism for autotransporter secretion.