Chervenak M C, Toone E J
Department of Chemistry, Duke University, Durham, NC 27708, USA.
Bioorg Med Chem. 1996 Nov;4(11):1963-77. doi: 10.1016/s0968-0896(96)00178-2.
The binding specificities of the closely related lectins from Canavalia ensiformis and Dioclea grandiflora were examined using specifically O-alkylated mono- and disaccharides. Both lectins accept any substitution at the monosaccharide C2 hydroxyl group. The binding energy of C2-alkylated ligands-concanavalin A complexes increases by 1 kcal mol-1 for the C2-O-ethyl ligand, while the binding energies of the corresponding complexes with the Dioclea lectin are identical. Both lectins accept methyl, but not ethyl, substitution of the C3 hydroxyl, in contrast to earlier reports. The results are interpreted in terms of existing models of the concanavalin A binding site. While the results are consistent with a model of the concanavalin A extended binding site that places the non-reducing terminus of all disaccharides in the monosaccharide binding site, they point to the dangers of interpreting the binding behavior of unnatural saccharide ligands on the basis of crystallographic data obtained with native ligands.
利用特定的O-烷基化单糖和二糖，研究了来自刀豆和大花蝶豆的亲缘关系密切的凝集素的结合特异性。两种凝集素都接受单糖C2羟基上的任何取代。对于C2-O-乙基配体，C2-烷基化配体-伴刀豆球蛋白A复合物的结合能增加1千卡/摩尔，而与大花蝶豆凝集素的相应复合物的结合能相同。与早期报道相反，两种凝集素都接受C3羟基的甲基取代，但不接受乙基取代。根据伴刀豆球蛋白A结合位点的现有模型对结果进行了解释。虽然结果与伴刀豆球蛋白A扩展结合位点的模型一致，该模型将所有二糖的非还原末端置于单糖结合位点，但它们指出了根据用天然配体获得的晶体学数据来解释非天然糖配体结合行为的危险性。
