Chervenak M C, Toone E J
Department of Chemistry, Duke University, Durham, North Carolina 27708-0346, USA.
Biochemistry. 1995 Apr 25;34(16):5685-95. doi: 10.1021/bi00016a045.
The thermodynamics of binding of a system of plant lectins specific for the oligosaccharide methyl 3,6-di-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside have been studied calorimetrically. This system of lectins consists of concanavalin A, the lectin isolated from Dioclea grandiflora, and the lectin from Galanthus nivalis. The group thus contains lectins with similar structures and similar binding properties as well as lectins with different structures but similar binding properties. Concanavalin A and the lectin from Dioclea are highly homologous, while the lectin from Galanthus nivalis shares no sequence homology with either of the legume lectins, although it also binds the mannose trisaccharide tightly. Calorimetric data for oligosaccharide binding to both of the legume lectins suggests that the total binding site comprises a single high-affinity site and an additional extended site. The pattern of binding for the lectin from Galanthus is significantly different. Binding studies with the same saccharides indicate that the lectin has binding sites designed specifically for the 1-->3 and 1-->6 arms of the mannose trisaccharide that are unable to accommodate other saccharides. Enthalpy--entropy compensation was observed for several saccharides as a function of lectin structure. Contributions of solvation effects to the enthalpy of binding and the configurational entropies were determined experimentally. For those systems studied here, solute-solute attractive interactions and configurational entropies were the greatest contributors to enthalpy-entropy compensation. Our studies clearly demonstrate that, despite their common affinity for the mannose trisaccharide, the three lectins bind oligosaccharides very differently.
已通过量热法研究了对寡糖甲基3,6 - 二 - O -（α - D - 甘露吡喃糖基）-α - D - 甘露吡喃糖苷具有特异性的植物凝集素系统的结合热力学。该凝集素系统由伴刀豆球蛋白A、从大花蝶豆中分离出的凝集素以及雪花莲凝集素组成。因此，该组包含结构相似且结合特性相似的凝集素，以及结构不同但结合特性相似的凝集素。伴刀豆球蛋白A和来自大花蝶豆的凝集素高度同源，而雪花莲凝集素与这两种豆科凝集素均无序列同源性，尽管它也能紧密结合甘露糖三糖。寡糖与两种豆科凝集素结合的量热数据表明，总结合位点包括一个高亲和力位点和一个额外的扩展位点。雪花莲凝集素的结合模式明显不同。对相同糖类的结合研究表明，该凝集素具有专门针对甘露糖三糖的1→3和1→6臂设计的结合位点，无法容纳其他糖类。观察到几种糖类作为凝集素结构的函数存在焓 - 熵补偿。通过实验确定了溶剂化效应对结合焓和构型熵的贡献。对于此处研究的那些系统，溶质 - 溶质吸引相互作用和构型熵是焓 - 熵补偿的最大贡献者。我们的研究清楚地表明，尽管这三种凝集素对甘露糖三糖具有共同的亲和力，但它们结合寡糖的方式非常不同。
