Mechanism of insertion of diphtheria toxin: peptide entry and pore size determinations.
Mechanism of insertion of diphtheria toxin: peptide entry and pore size determinations.
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白喉毒素的插入机制：肽进入和孔径测定。
DOI：
10.1073/pnas.81.11.3341
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发表时间：
1984
影响因子：
11.1
通讯作者：
Wisnieski,BJ
中科院分区：
文献类型：
--
作者：
Zalman,LS;Wisnieski,BJ
白喉毒素（DTx）是一种非常有效的蛋白质合成抑制剂。作为线性多肽分泌，裂解产生二硫键连接的A和B片段。片段A是蛋白质合成的抑制剂，需要片段B（识别亚基）才能进入完整的细胞。片段B已被提出形成跨膜通道，通过该通道A进入胞质溶胶。如果证明B亚基只与膜脂酰基链结合，这可能表明A被隔离在蛋白质B通道中。然而，我们的结果从膜内的光标记研究表明，这两个亚基的DTx进入烃结构域的双层。穿透不需要毒素裂解。降低pH值导致结合增加，从而间接增加渗透。平行渗透性研究表明，裂解的DTx确实形成孔（直径24 A），并且它们大于先前报道的天然毒素的孔（5 A）。数据表明这些是二聚体结构。裂解的DTx在孔形成方面比完整的DTx有效得多。因此，我们的结论是，虽然孔形成是一个特点的毒素膜相互作用，孔结构不保护A与脂质侧链接触，实际上可能由A和B域的二聚体配置，（AB）2。
Diphtheria toxin ( DTx ) is an extremely potent inhibitor of protein synthesis. It is secreted as a linear polypeptide, which is cleaved to produce disulfide-linked A and B fragments. Fragment A, the inhibitor of protein synthesis, requires fragment B, the recognition subunit, for entry into intact cells. Fragment B has been proposed to form a transmembrane channel through which A gains access to the cytosol. If it were demonstrated that the B subunit had an exclusive association with membrane lipid acyl chains, this might indicate that A is secluded in a proteinaceous B channel. However, our results from intramembranous photolabeling studies show that both subunits of DTx enter the hydrocarbon domain of the bilayer. Toxin cleavage is not required for penetration. Decreasing pH leads to increased binding and hence indirectly to increased penetration. Parallel permeability studies indicate that cleaved DTx does indeed form pores (24 A in diameter) and they are larger than those previously reported (5 A) with native toxin. The data suggest that these are dimeric structures. Cleaved DTx is much more effective than intact DTx at pore formation. Thus, we conclude that, while pore formation is a feature of toxin-membrane interaction, the pore structure does not protect A from contact with lipid side chains and may in fact consist of both the A and B domains in a dimeric configuration, (AB)2.