Wu A M, Wu J H, Tsai M S, Kaltner H, Gabius H J
Glyco-Immunochemistry Research Laboratory, Institute of Molecular and Cellular Biology, College of Medicine, Chang-Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-yuan 333, Taiwan.
Biochem J. 2001 Sep 15;358(Pt 3):529-38. doi: 10.1042/0264-6021:3580529.
Owing to the expression of more than one type of galectin in animal tissues, the delineation of the functions of individual members of this lectin family requires the precise definition of their carbohydrate specificities. Thus, the binding properties of chicken liver galectin (CG-16) to glycoproteins (gps) and Streptococcus pneumoniae type 14 polysaccharide were studied by the biotin/avidin-mediated microtitre-plate lectin-binding assay and by the inhibition of lectin-glycan interactions with sugar ligands. Among 33 glycans tested for lectin binding, CG-16 reacted best with human blood group ABO (H) precursor gps and their equivalent gps, which contain a high density of D-galactopyranose(beta1-4)2-acetamido-2-deoxy-D-glucopyranose [Gal(beta1-4)GlcNAc] and Gal(beta1-3)GlcNAc residues at the non-reducing end, but this lectin reacted weakly or not at all with A-,H-type and sialylated gps. Among the oligosaccharides tested by the inhibition assay, the tri-antennary Gal(beta1-4)GlcNAc (Tri-II) was the best. It was 2.1x10(3) nM and 3.0 times more potent than Gal and Gal(beta1-4)GlcNAc (II)/Gal(beta1-3)GlcNAc(beta1-3)Gal(beta1-4)Glc (lacto-N-tetraose) respectively. CG-16 has a preference for the beta-anomer of Gal at the non-reducing end of oligosaccharides with a Gal(beta1-4) linkage >Gal(beta1-3)> or =Gal(beta1-6). From the results, it can be concluded that the combining site of this agglutinin should be a cavity type, and that a hydrophobic interaction in the vicinity of the binding site for sugar accommodation increases the affinity. The binding site of CG-16 is as large as a tetrasaccharide of the beta-anomer of Gal, and is most complementary to lacto-N-tetraose and Gal(beta1-4)GlcNAc related sequences.
由于动物组织中存在多种半乳糖凝集素，要明确该凝集素家族各成员的功能，就需要精确界定它们的碳水化合物特异性。因此，通过生物素/抗生物素蛋白介导的微量滴定板凝集素结合试验以及用糖配体抑制凝集素 - 聚糖相互作用，研究了鸡肝半乳糖凝集素（CG - 16）与糖蛋白（gps）和14型肺炎链球菌多糖的结合特性。在测试的33种与凝集素结合的聚糖中，CG - 16与人类血型ABO（H）前体糖蛋白及其等效糖蛋白反应最佳，这些糖蛋白在非还原端含有高密度的D - 吡喃半乳糖（β1 - 4）2 - 乙酰氨基 - 2 - 脱氧 - D - 吡喃葡萄糖[Gal（β1 - 4）GlcNAc]和Gal（β1 - 3）GlcNAc残基，但该凝集素与A - 、H型和唾液酸化糖蛋白反应较弱或根本不反应。在抑制试验测试的寡糖中，三分支的Gal（β1 - 4）GlcNAc（Tri - II）效果最佳。其浓度为2.1×10³ nM，分别比Gal和Gal（β1 - 4）GlcNAc（II）/Gal（β1 - 3）GlcNAc（β1 - 3）Gal（β1 - 4）Glc（乳糖 - N - 四糖）强3.0倍。CG - 16优先结合具有Gal（β1 - 4）连接＞Gal（β1 - 3）＞或 = Gal（β1 - 6）的寡糖非还原端的Galβ异头物。从结果可以得出结论，这种凝集素的结合位点应为腔型，并且在结合位点附近用于容纳糖的疏水相互作用增加了亲和力。CG - 16的结合位点与Galβ异头物的四糖一样大，并且与乳糖 - N - 四糖和Gal（β1 - 4）GlcNAc相关序列最互补。
