André S, Ortega P J, Perez M A, Roy R, Gabius H J
Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians-University, Veterinärstrasse 13, D-80539 Munich, Germany.
Glycobiology. 1999 Nov;9(11):1253-61. doi: 10.1093/glycob/9.11.1253.
Starburst glycodendrimers offer the potential to serve as high-affinity ligands for clinically relevant sugar receptors. In order to define areas of application, their binding behavior towards sugar receptors with differential binding-site orientation but identical monosaccharide specificity must be evaluated. Using poly(amidoamine) starburst dendrimers of five generations, which contain the p-isothiocyanato derivative of p-aminophenyl-beta-D-lactoside as ligand group, four different types of galactoside-binding proteins were chosen for this purpose, i.e., the (AB)(2)-toxic agglutinin from mistletoe, a human immunoglobulin G fraction, the homodimeric galectin-1 with its two binding sites at opposite ends of the jelly-roll-motif-harboring protein and monomeric galectin-3. Direct solid-phase assays with surface-immobilized glycodendrimers resulted in obvious affinity enhancements by progressive core branching for the plant agglutinin and less pronounced for the antibody and galectin-1. High density of binding of galectin-3 with modest affinity increases only from the level of the 32-mer onwards points to favorable protein-protein interactions of the monomeric lectin and a spherical display of the end groups without a major share of backfolding. When the inhibitory potency of these probes was evaluated as competitor of receptor binding to an immobilized neoglycoprotein or to asialofetuin, a marked selectivity was detected. The 32- and 64-mers were second to none as inhibitors for the plant agglutinin against both ligand-exposing matrices and for galectin-1 on the matrix with a heterogeneous array of interglycoside distances even on the per-sugar basis. In contrast, a neoglycoprotein with the same end group was superior in the case of the antibody and, less pronounced, monomeric galectin-3. Intimate details of topological binding-site presentation and the ligand display on different generations of core assembly are major operative factors which determine the potential of dendrimers for applications as lectin-targeting device, as attested by these observations.
星爆型糖树状大分子有潜力作为临床相关糖受体的高亲和力配体。为了确定其应用领域，必须评估它们与具有不同结合位点取向但单糖特异性相同的糖受体的结合行为。为此，使用了五代聚（酰胺胺）星爆型树状大分子，其含有对氨基苯基-β-D-乳糖苷的对异硫氰酸酯衍生物作为配体基团，选择了四种不同类型的半乳糖苷结合蛋白，即来自槲寄生的（AB）₂毒性凝集素、人免疫球蛋白G组分、在具有果冻卷基序的蛋白两端具有两个结合位点的同型二聚体半乳糖凝集素-1和单体半乳糖凝集素-3。用表面固定的糖树状大分子进行直接固相分析，结果表明，对于植物凝集素，随着核心分支的增加，亲和力明显增强；对于抗体和半乳糖凝集素-1，亲和力增强不太明显。半乳糖凝集素-3以适度亲和力的高密度结合仅从32聚体水平开始增加，这表明单体凝集素具有良好的蛋白质-蛋白质相互作用，且端基呈球形展示，没有大量的反向折叠。当评估这些探针作为受体与固定化新糖蛋白或去唾液酸胎球蛋白结合的竞争者的抑制效力时，检测到明显的选择性。32聚体和64聚体作为植物凝集素对两种配体暴露基质的抑制剂以及对具有异质糖苷间距阵列的基质上的半乳糖凝集素-1的抑制剂，即使以每个糖为基础也是首屈一指的。相比之下，具有相同端基的新糖蛋白在抗体以及不太明显的单体半乳糖凝集素-3的情况下更具优势。这些观察结果证明，拓扑结合位点呈现和不同代核心组装上的配体展示的详细细节是决定树状大分子作为凝集素靶向装置应用潜力的主要操作因素。
