The carbohydrate-binding promiscuity of Euonymus europaeus lectin is predicted to involve a single binding site
The carbohydrate-binding promiscuity of Euonymus europaeus lectin is predicted to involve a single binding site
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DOI：
10.1093/glycob/cwu095
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发表时间：
2015-01-01
期刊：
影响因子：
4.3
通讯作者：
Ramsland, Paul A.
中科院分区：
文献类型：
--
作者：
Agostino, Mark;Velkov, Tony;Ramsland, Paul A.
欧洲卫矛凝集素 (EEL) 是一种源自欧洲纺锤树果实的碳水化合物结合蛋白。 EEL 最初因其红细胞凝集特性以及对 B 和 H 血型的特异性而被鉴定。然而，EEL 识别碳水化合物的结构基础的详细分子图谱仍有待开发。在这项研究中，我们针对 EEL 对一系列碳水化合物进行了荧光滴定。观察到EEL与多种碳水化合物结合，包括一系列与血型相关的碳水化合物、甘露糖苷、壳三糖和唾液酸。具有 H 相关结构的碳水化合物和 B 三糖的亲和力最强。 EEL 的同源模型是根据使用 HHPred 服务器识别的模板生成的，该服务器采用隐马尔可夫模型 (HMM) 来识别模板。 HMM 方法确定 EEL 的最佳模板是具有蓖麻毒素 B 样（R 型）折叠特征的蛋白质。使用单独的模板来模拟凝集素的核心和结合位点区域。通过使用约束对接和与模板配体的空间比较，预测了碳水化合物配体的结合模式。确定并优化了所选对接姿势的实验结合能和计算的结合能之间的关系。总的来说，我们的结果表明 EEL 利用单个位点来识别以各种单糖结尾的碳水化合物。
Euonymus europaeus lectin (EEL) is a carbohydrate-binding protein derived from the fruit of the European spindle tree. EEL was first identified for its erythrocyte agglutinating properties and specificity for B and H blood groups. However, a detailed molecular picture of the structural basis of carbohydrate recognition by EEL remains to be developed. In this study, we performed fluorescence titrations of a range of carbohydrates against EEL. Binding of EEL to a wide range of carbohydrates was observed, including a series of blood group-related carbohydrates, mannosides, chitotriose and sialic acid. Affinity was strongest for carbohydrates with H-related structures and the B trisaccharide. A homology model of EEL was produced from templates identified using the HHPred server, which employs hidden Markov models (HMMs) to identify templates. The HMM approach identified that the best templates for EEL were proteins featuring a ricin B-like (R-type) fold. Separate templates were used to model the core and binding site regions of the lectin. Through the use of constrained docking and spatial comparison with a template ligand, binding modes for the carbohydrate ligands were predicted. A relationship between the experimental binding energies and the computed binding energies of the selected docked poses was determined and optimized. Collectively, our results suggest that EEL utilizes a single site for recognition of carbohydrates terminating in a variety of monosaccharides.