Ivatt R J, Reeder J W, Clark G F
Biochim Biophys Acta. 1986 Sep 4;883(2):253-64. doi: 10.1016/0304-4165(86)90316-8.
We examined the interaction between immobilized wheat germ agglutinin and the large, polylactosamine-containing glycans from human erythrocytes and human K-562 erythroleukemic cells. Three classes of interaction were identified. One class of glycan was merely retarded during chromatography. The other two classes were retained and could be distinguished by their ease of displacement with N-acetylglucosamine (GlcNAc); one was a moderate-affinity fraction displaced by 0.1 M GlcNAc and the other was a high-affinity fraction subsequently displaced by 1.0 M GlcNAc. A relatively small fraction of the K-562 polylactosamines were in the high-affinity class. We explored the role that fucose and sialic acid substitutions play in the strength of the lectin-glycan interaction. Although sialic acid is recognized by wheat germ agglutinin, sialylation was not required for the high-affinity interaction, and the presence of sialic acids actually prevented some glycans from binding with high affinity. In contrast, fucose is not part of the binding determinant, yet the removal of fucose resulted in decreased affinity. The possibility that some of these changes in affinity were the result of conformational changes was explored using matrices that had wheat germ agglutinin immobilized at different densities. At low wheat germ agglutinin densities, adult and fetal erythroglycans and K-562 glycophorin-like glycans were not retained by the matrix. As the density increased, the proportion of glycans that were retarded, and ultimately retained, increased. While these increases in the proportions retained occurred in parallel for the three different glycans, the apparent affinities of the glycan-lectin interactions differed. The glycophorin-like glycans were always readily displaced by 0.1 M GlcNAc, even at higher wheat germ agglutinin densities. In contrast, as the wheat germ agglutinin density increased, the proportion of erythroglycans that could be displaced by 0.1 M GlcNAc decreased; at 10 mg/ml immobilized wheat germ agglutinin, greater than 80% of the erythroglycans exhibited this tighter interaction. We suggest that this higher affinity interaction is the result of the large glycans spanning adjacent wheat germ agglutinin molecules, and is determined by the proximity of these molecules and the conformation of the glycans.
我们研究了固定化麦胚凝集素与来自人红细胞和人K - 562红白血病细胞的含多聚乳糖胺的大聚糖之间的相互作用。确定了三类相互作用。一类聚糖在色谱过程中仅仅是迁移速度减慢。另外两类被保留，并且可以通过它们被N - 乙酰葡糖胺（GlcNAc）置换的难易程度来区分；一类是被0.1 M GlcNAc置换的中等亲和力部分，另一类是随后被1.0 M GlcNAc置换的高亲和力部分。K - 562多聚乳糖胺中相对较小的一部分属于高亲和力类别。我们探究了岩藻糖和唾液酸取代在凝集素 - 聚糖相互作用强度中所起的作用。尽管唾液酸能被麦胚凝集素识别，但高亲和力相互作用并不需要唾液酸化，而且唾液酸的存在实际上阻止了一些聚糖以高亲和力结合。相反，岩藻糖不是结合决定簇的一部分，但去除岩藻糖会导致亲和力降低。使用固定有不同密度麦胚凝集素的基质探究了这些亲和力变化部分是由构象变化导致的可能性。在低麦胚凝集素密度下，成人和胎儿红细胞聚糖以及K - 562血型糖蛋白样聚糖不会被基质保留。随着密度增加，迁移速度减慢并最终被保留的聚糖比例增加。虽然这三种不同聚糖被保留的比例增加是平行发生的，但聚糖 - 凝集素相互作用的表观亲和力不同。即使在较高的麦胚凝集素密度下，血型糖蛋白样聚糖总是很容易被0.1 M GlcNAc置换。相反，随着麦胚凝集素密度增加，能被0.1 M GlcNAc置换的红细胞聚糖比例降低；在固定化麦胚凝集素浓度为10 mg/ml时，超过80%的红细胞聚糖表现出这种更强的相互作用。我们认为这种更高亲和力的相互作用是大聚糖跨越相邻麦胚凝集素分子的结果，并且由这些分子的接近程度和聚糖的构象决定。
