The major toxin from the Australian Common Brown Snake is a hexamer with unusual gas-phase dissociation properties
The major toxin from the Australian Common Brown Snake is a hexamer with unusual gas-phase dissociation properties
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DOI：
10.1002/prot.22259
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发表时间：
2009-05-01
影响因子：
2.9
通讯作者：
Aquilina, J. Andrew
中科院分区：
文献类型：
--
作者：
Aquilina, J. Andrew
多电荷蛋白质组装体的不对称解离已被频繁报道。这种现象依赖于一种或多种高电荷单体的解离，已被证明可以深入了解大型单分散和多分散组装体的结构和组织。在这里，不对称解离的过程中使用的多亚基蛋白质，textilotoxin，它具有异常高的结构限制，由于其单体的多个二硫键。最初，它表明，与以前的报告，textilotoxin是由六个，而不是五个亚基。此外，六聚体以两种同种型存在，其中一种基本上更加糖基化。对六聚体的气相解离研究揭示了每种亚型的亚基化学计量为（A/B）（2）C2 D2 a和（A/B）CD 2aD 2B b，其中A和B是质量非常相似的亚基，D-2a、D-2 B是指D亚基的差异糖基化二聚体。解离的机制是不寻常的，而不是一个亚基被大量删除之前，顺序解离的第二个，该过程主要是并发的两个最小的亚基。此外，观察到一小部分解离的物质是非共价缔合的二聚体。相同textilotoxin同种型的两个相邻电荷状态的解离途径的比较表明，与以前的报告一致，四级结构的变化是负责蛋白质的不同电荷状态。
Asymmetric dissociation of multiply charged protein assemblies has been frequently reported. This phenomenon, which relies on the dissociation of one or more highly charged monomers, has been shown to provide insights into the structure and organization of large monodisperse and polydisperse assemblies. Here, the process of asymmetric dissociation is investigated using the multisubunit protein, textilotoxin, which has unusually high structural constraints on its monomers due to multiple disulfide linkages. Initially, it is shown that, contrary to previous reports, textilotoxin is made up of six, rather than five subunits. Furthermore, the hexamer exists as two isoforms, one of which is substantially more glycosylated. Gas-phase dissociation studies on the hexamers reveal the subunit stoichiometry of each isoform to be (A/B)(2)C2D2a and (A/B)CD2aD2b, where A and B are subunits of very similar mass and D-2a, D-2b refer to differentially glycosylated dimers of the D subunit. The mechanism of dissociation was unusual, as rather than one subunit being largely removed before sequential dissociation of a second, the process was predominantly concurrent for the two smallest subunits. Furthermore, a small proportion of the dissociated species was observed to be a noncovalently associated dimer. A comparison of dissociation pathways for two neighboring charge states of the same textilotoxin isoform demonstrates that, in agreement with previous reports, variations in quaternary structure are responsible for the distinct charge states of a protein.