Cummings M D, Ling H, Armstrong G D, Brunton J L, Read R J
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Biochemistry. 1998 Feb 17;37(7):1789-99. doi: 10.1021/bi971807f.
The wild-type binding pentamer of Shiga-like toxin IIe (SLT-IIe) binds both the globotriaosylceramide (Gb3) and globotetraosylceramide (Gb4) cell surface glycolipids, whereas the double mutant GT3 (Q65E/K67Q) exhibits a marked preference for Gb3 [Tyrrell, G. J., et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 524-528]. We modeled three unique sites (sites 1-3) for binding of the carbohydrate moiety of Gb3 to GT3 and SLT-IIe, on the basis of the three sites observed for the SLT-I pentamer [Ling, H., et al. (1998) Biochemistry 37, 1777-1788]. Examination of the three sites in light of various mutation and binding data strongly suggested that one of the binding sites plays a role in the change of specificity observed for the GT3 mutant. We applied several modeling techniques, and developed a model for binding of the carbohydrate moiety of Gb4 to this site of the SLT-IIe binding pentamer. This model is consistent with a wide variety of mutation and binding data and clearly shows the importance of the terminal GalNAc residue of Gb4, as well as that of the two mutated residues of GT3, to the intermolecular interaction.
志贺样毒素IIe（SLT-IIe）的野生型结合五聚体可结合球三糖神经酰胺（Gb3）和球四糖神经酰胺（Gb4）这两种细胞表面糖脂，而双突变体GT3（Q65E/K67Q）对Gb3表现出明显的偏好[泰瑞尔，G. J.等人（1992年）《美国国家科学院院刊》89，524 - 528]。基于在SLT-I五聚体中观察到的三个位点[凌，H.等人（1998年）《生物化学》37，1777 - 1788]，我们构建了Gb3碳水化合物部分与GT3和SLT-IIe结合的三个独特位点（位点1 - 3）的模型。根据各种突变和结合数据对这三个位点进行研究，强烈表明其中一个结合位点在GT3突变体所观察到的特异性变化中起作用。我们应用了几种建模技术，并构建了一个Gb4碳水化合物部分与SLT-IIe结合五聚体该位点结合的模型。该模型与各种突变和结合数据一致，并且清楚地显示了Gb4的末端GalNAc残基以及GT3的两个突变残基对分子间相互作用的重要性。
