Wu Albert M, Singh Tanuja, Wu June H, Lensch Martin, André Sabine, Gabius Hans-Joachim
Glyco-Immunochemistry Research Laboratory, Institute of Molecular and Cellular Biology, Chang-Gung University, Kwei-san, Tao-yuan, 333, Taiwan.
Glycobiology. 2006 Jun;16(6):524-37. doi: 10.1093/glycob/cwj102. Epub 2006 Mar 15.
Cell-surface glycans are functional docking sites for tissue lectins such as the members of the galectin family. This interaction triggers a wide variety of responses; hence, there is a keen interest in defining its structural features. Toward this aim, we have used enzyme-linked lectinosorbent (ELLSA) and inhibition assays with the prototype rat galectin-5 and panels of free saccharides and glycoconjugates. Among 45 natural glycans tested for lectin binding, galectin-5 reacted best with glycoproteins (gps) presenting a high density of Galbeta1-3/4GlcNAc (I/II) and multiantennary N-glycans with II termini. Their reactivities, on a nanogram basis, were up to 4.3 x 10(2), 3.2 x 10(2), 2.5 x 10(2), and 1.7 x 10(4) times higher than monomeric Galbeta1-3/4GlcNAc (I/II), triantennary-II (Tri-II), and Gal, respectively. Galectin-5 also bound well to several blood group type B (Galalpha1-3Gal)- and A (GalNAcalpha1-3Gal)-containing gps. It reacted weakly or not at all with tumor-associated Tn (GalNAcalpha1-Ser/Thr) and sialylated gps. Among the mono-, di-, and oligosaccharides and mammalian glycoconjugates tested, blood group B-active II (Galalpha1-3Gal beta1-4GlcNAc), B-active IIbeta1-3L (Galalpha1-3Galbeta1-4GlcNAc beta1-3Galbeta1-4Glc), and Tri-II were the best. It is concluded that (1) Galbeta1-3/4GlcNAc and other Galbeta1-related oligosaccharides with alpha1-3 extensions are essential for binding, their polyvalent form in cellular glycoconjugates being a key recognition force for galectin-5; (2) the combining site of galectin-5 appears to be of a shallow-groove type sufficiently large to accommodate a substituted beta-galactoside, especially with alpha-anomeric extension at the non-reducing end (e.g., human blood group B-active II and B-active IIbeta1-3L); (3) the preference within beta-anomeric positioning is Galbeta1-4 > or = Galbeta1-3 > Galbeta1-6; and (4) hydrophobic interactions in the vicinity of the core galactose unit can enhance binding. These results are important for the systematic comparison of ligand selection in this family of adhesion/growth-regulatory effectors with potential for medical applications.
细胞表面聚糖是组织凝集素（如半乳糖凝集素家族成员）的功能性对接位点。这种相互作用引发了各种各样的反应；因此，人们对确定其结构特征有着浓厚的兴趣。为了实现这一目标，我们使用了酶联凝集素吸附测定法（ELLSA）以及与原型大鼠半乳糖凝集素-5、游离糖类和糖缀合物进行的抑制试验。在测试的45种天然聚糖中，半乳糖凝集素-5与呈现高密度Galβ1-3/4GlcNAc（I/II）和具有II型末端的多天线N-聚糖的糖蛋白（gp）反应最佳。以纳克为基础，它们的反应活性分别比单体Galβ1-3/4GlcNAc（I/II）、三天线-II（Tri-II）和Gal高4.3×10²、3.2×10²、2.5×10²和1.7×10⁴倍。半乳糖凝集素-5也能很好地结合几种含有B血型（Galα1-3Gal）和A血型（GalNAcα1-3Gal）的gp。它与肿瘤相关的Tn（GalNAcα1-Ser/Thr）和唾液酸化的gp反应较弱或根本不反应。在测试的单糖、二糖、寡糖和哺乳动物糖缀合物中，B血型活性II（Galα1-3Galβ1-4GlcNAc）、B活性IIβ1-3L（Galα1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glc）和Tri-II是最佳的。得出以下结论：（1）Galβ1-3/4GlcNAc和其他具有α1-3延伸的Galβ1相关寡糖对于结合至关重要，它们在细胞糖缀合物中的多价形式是半乳糖凝集素-5的关键识别力；（2）半乳糖凝集素-5的结合位点似乎是浅槽型，足够大以容纳取代的β-半乳糖苷，特别是在非还原端具有α-异头延伸的情况（例如，人B血型活性II和B活性IIβ1-3L）；（3）β-异头定位内的偏好是Galβ1-4≥Galβ1-3＞Galβ1-6；（4）核心半乳糖单元附近的疏水相互作用可以增强结合。这些结果对于系统比较这一具有潜在医学应用的粘附/生长调节效应器家族中的配体选择非常重要。
