Structural basis for pore-forming mechanism of staphylococcal α-hemolysin
Structural basis for pore-forming mechanism of staphylococcal α-hemolysin
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DOI：
10.1016/j.toxicon.2015.09.033
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发表时间：
2015-12-15
期刊：
影响因子：
2.8
通讯作者：
Yao, Min
中科院分区：
文献类型：
--
作者：
Sugawara, Takaki;Yamashita, Daichi;Yao, Min
葡萄球菌α-溶血素（α-HL）是一种由金黄色葡萄球菌表达的β-桶孔形成毒素（PFT）。α-HL作为水溶性单体蛋白分泌，其结合靶膜并形成插入膜的七聚体孔。为了详细探讨α-HL的成孔机制，我们分别测定了H35 A突变体和W179 A/R200 A突变体的α-HL单体和前孔的晶体结构。虽然单体的整体结构与其他葡萄球菌PFT相似，但在N-末端氨基锁存器中观察到显著差异，其向prestem弯曲。此外，prestem是由帽结构域与Asp 45和Tyr 118之间的关键氢键紧固。peptide结构表明，尽管β-桶的上半部分适当地形成，但跨膜区大致形成为具有柔性。单体、前孔和孔之间的结构比较揭示了一系列运动，其中寡聚化后释放的N-末端氨基闩锁破坏了Asp 45 Tyr 118之间的关键氢键。这个动作引发了前茎的突出。Y118 F突变体和N端截短突变体的溶血活性明显降低，表明关键氢键和N端氨基闩锁在孔形成中的重要性。基于这些观察结果，我们提出了一个动态的分子机制的α-HL孔形成。(C)2015爱思唯尔有限公司版权所有。
Staphylococcal alpha-hemolysin (alpha-HL) is a beta-barrel pore-forming toxin (PFT) expressed by Staphylococcus aureus. alpha-HL is secreted as a water-soluble monomeric protein, which binds to target membranes and forms membrane-inserted heptameric pores. To explore the pore-forming mechanism of alpha-HL in detail, we determined the crystal structure of the alpha-HL monomer and prepore using H35A mutant and W179A/R200A mutant, respectively. Although the overall structure of the monomer was similar to that of other staphylococcal PFTs, a marked difference was observed in the N-terminal amino latch, which bent toward the prestem. Moreover, the prestem was fastened by the cap domain with a key hydrogen bond between Asp45 and Tyr118. Prepore structure showed that the transmembrane region is roughly formed with flexibility, although the upper half of the beta-barrel is formed appropriately. Structure comparison among monomer, prepore and pore revealed a series of motions, in which the N-terminal amino latch released upon oligomerization destroys its own key hydrogen bond between Asp45 Tyr118. This action initiated the protrusion of the prestem. Y118F mutant and the N-terminal truncated mutant markedly decreased in the hemolytic activity, indicating the importance of the key hydrogen bond and the N-terminal amino latch on the pore formation. Based on these observations, we proposed a dynamic molecular mechanism of pore formation for alpha-HL. (C) 2015 Elsevier Ltd. All rights reserved.