Structure and action of the binary C2 toxin from Clostridium botulinum.
Structure and action of the binary C2 toxin from Clostridium botulinum.
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DOI：
10.1016/j.jmb.2006.09.002
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发表时间：
2006-12
影响因子：
5.6
通讯作者：
C. Schleberger;Henrike Hochmann;H. Barth;K. Aktories;G. Schulz
中科院分区：
文献类型：
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作者：
C. Schleberger;Henrike Hochmann;H. Barth;K. Aktories;G. Schulz
肉毒梭菌C2毒素由酶组分C2-I和结合和转位组分C2-II组成，所述酶组分C2-I使肌动蛋白ADP-核糖基化，所述结合和转位组分C2-II负责与真核细胞受体的相互作用和随后的内吞作用。三个C2-I晶体结构的分辨率高达1.75 μ m，与C2-II的晶体结构在一个明显较低的分辨率和一个模型的预孔形成的片段C2-IIa。在pH 3.0和pH 6.1下测定C2-I结构。结构差异很小，表明即使在低至3.0的pH值下，C2-I也不会展开。测定了C2-I的ADP-核糖基转移酶活性（α和β/γ-肌动蛋白），并与Iota毒素和引入Iota毒素中观察到的精氨酸的C2-I突变体S361 R的ADP-核糖基转移酶活性相关。α-肌动蛋白和β/γ-肌动蛋白之间的活性差异不能用现有的蛋白质结构来解释。使用pH 6.0的炭疽毒素保护性抗原模型，通过分子置换建立了pH 4.3的转运组分C2-II的结构。C2-II的C-末端受体结合结构域无法定位，但存在于晶体中。它可以是移动的。C2-II的其他四个结构域的相对方向和位置与保护性抗原的相对方向和位置没有太大差异，表明在pH 4.3和pH 6.0之间没有发生大的构象变化。基于保护性抗原的相应组装，构建了C2-IIa前孔结构的模型。它揭示了令人惊讶的大量天冬酰胺残基内衬孔。对C2-I与C2-IIa的相互作用及C2-I向靶细胞的转位进行了讨论。
C2 toxin from Clostridium botulinum is composed of the enzyme component C2-I, which ADP-ribosylates actin, and the binding and translocation component C2-II, responsible for the interaction with eukaryotic cell receptors and the following endocytosis. Three C2-I crystal structures at resolutions of up to 1.75 Å are presented together with a crystal structure of C2-II at an appreciably lower resolution and a model of the prepore formed by fragment C2-IIa. The C2-I structure was determined at pH 3.0 and at pH 6.1. The structural differences are small, indicating that C2-I does not unfold, even at a pH value as low as 3.0. The ADP-ribosyl transferase activity of C2-I was determined for α and β/γ-actin and related to that of Iota toxin and of mutant S361R of C2-I that introduced the arginine observed in Iota toxin. The substantial activity differences between α and β/γ-actin cannot be explained by the protein structures currently available. The structure of the transport component C2-II at pH 4.3 was established by molecular replacement using a model of the protective antigen of anthrax toxin at pH 6.0. The C-terminal receptor-binding domain of C2-II could not be located but was present in the crystals. It may be mobile. The relative orientation and positions of the four other domains of C2-II do not differ much from those of the protective antigen, indicating that no large conformational changes occur between pH 4.3 and pH 6.0. A model of the C2-IIa prepore structure was constructed based on the corresponding assembly of the protective antigen. It revealed a surprisingly large number of asparagine residues lining the pore. The interaction between C2-I and C2-IIa and the translocation of C2-I into the target cell are discussed.