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首页> 外文期刊>Journal of Molecular Biology >Solution structure of the eukaryotic pore-forming cytolysin equinatoxin II: implications for pore formation.
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Solution structure of the eukaryotic pore-forming cytolysin equinatoxin II: implications for pore formation.

机译：真核孔形成细胞溶素马匹毒素II的溶液结构：对孔形成的影响。

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Sea anemones produce a family of 18-20 kDa proteins, the actinoporins, that lyse cells by forming pores in cell membranes. Sphingomyelin plays an important role in their lytic activity, with membranes lacking this lipid being largely refractory to these toxins. The structure of the actinoporin equinatoxin II in aqueous solution, determined from NMR data, consists of two short helices packed against opposite faces of a beta-sandwich structure formed by two five-stranded beta-sheets. The protein core has extensive hydrophobic interfaces formed by residues projecting from the internal faces of the two beta-sheets. 15N relaxation data show uniform backbone dynamics, implying that equinatoxin II in solution is relatively rigid, except at the N terminus; its inferred rotational correlation time is consistent with values for monomeric proteins of similar mass. Backbone amide exchange rate data also support the view of a stable structure, even though equinatoxin II lacks disulfide bonds. As monitored by NMR, it unfolds at around 70 degrees C at pH 5.5. At 25 degrees C the structure is stable over the pH range 2.5-7.3 but below pH 2.5 it undergoes a slow transition to an incompletely unfolded structure resembling a molten globule. Equinatoxin II has two significant patches of positive electrostatic potential formed by surface-exposed Lys and Arg residues, which may assist its interaction with charged regions of the lipid head groups. Tyr and Trp residues on the surface may also contribute by interacting with the carbonyl groups of the acyl chains of target membranes. Data from mutational studies and truncated analogues identify two regions of the protein involved in membrane interactions, the N-terminal helix and the Trp-rich region. Once the protein is anchored, the N-terminal helix may penetrate the membrane, with up to four helices lining the pore, although other mechanisms of pore formation cannot be ruled out.
机译：海葵产生18-20 kDa的蛋白质（肌动孔蛋白）家族，通过在细胞膜上形成孔来裂解细胞。鞘磷脂在其裂解活性中起重要作用，缺乏这种脂质的膜对这些毒素具有很大的抵抗力。根据NMR数据确定的放线菌素马匹毒素II在水溶液中的结构由两个短螺旋组成，两个短螺旋堆积在由两个五链β-折叠形成的β-三明治结构的相对表面上。蛋白质核心具有广泛的疏水性界面，该界面由从两个β-折叠片的内表面伸出的残基形成。 15N弛豫数据显示均匀的骨架动力学，这意味着溶液中的马鞭毛毒素II相对较硬，但N端除外。其推断的旋转相关时间与相似质量的单体蛋白质的值一致。即使马毒素II缺乏二硫键，主链酰胺交换率数据也支持稳定结构的观点。如通过NMR监测的，其在pH 5.5在约70℃下展开。在25摄氏度时，该结构在pH值2.5-7.3范围内是稳定的，但是在pH值2.5以下时，它会缓慢过渡到未完全展开的结构，类似于熔融小球。 Equinatoxin II具有两个显着的由表面暴露的Lys和Arg残基形成的正静电势斑，这可能有助于其与脂质头基的带电区域相互作用。表面上的Tyr和Trp残基也可能通过与目标膜的酰基链的羰基相互作用而起作用。来自突变研究和截短的类似物的数据确定了参与膜相互作用的蛋白质的两个区域，即N末端螺旋和富含Trp的区域。一旦蛋白质被锚定，N-末端螺旋可能会穿透膜，最多四个螺旋排列在孔中，尽管不能排除其他形成孔的机制。

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