PDF(Pubmed)
Abstract：
The dimeric architecture of tandem-repeat type galectins, such as galectin-4 (Gal-4), modulates their biological activities, although the underlying molecular mechanisms have remained elusive. Emerging evidence show that tandem-repeat galectins play an important role in innate immunity by recognizing carbohydrate antigens present on the surface of certain pathogens, which very often mimic the structures of the human self-glycan antigens. Herein, we have analyzed the binding preferences of the C-domain of Gal-4 (Gal-4C) toward the ABH-carbohydrate histo-blood antigens with different core presentations and their recognition features have been rationalized by using a combined experimental approach including NMR, solid-phase and hemagglutination assays, and molecular modeling. The data show that Gal-4C prefers A over B antigens (two-fold in affinity), contrary to the N-domain (Gal-4N), although both domains share the same preference for the type-6 presentations. The behavior of the full-length Gal-4 (Gal-4FL) tandem-repeat form has been additionally scrutinized. Isothermal titration calorimetry and NMR data demonstrate that both domains within full-length Gal-4 bind to the histo-blood antigens independently of each other, with no communication between them. In this context, the heterodimeric architecture does not play any major role, apart from the complementary A and B antigen binding preferences. However, upon binding to a bacterial lipopolysaccharide containing a multivalent version of an H-antigen mimetic as O-antigen, the significance of the galectin architecture was revealed. Indeed, our data point to the linker peptide domain and the F-face of the C-domain as key elements that provide Gal-4 with the ability to cross-link multivalent ligands, beyond the glycan binding capacity of the dimer.
摘要：
串联重复型半乳糖凝集素的二聚体结构，如半乳糖凝集素-4（Gal-4），调节它们的生物活性，尽管潜在的分子机制仍然难以捉摸。新的证据表明，串联重复半乳糖凝集素通过识别某些病原体表面存在的碳水化合物抗原在先天免疫中起重要作用。经常模拟人类自身聚糖抗原的结构。在这里，我们已经分析了Gal-4（Gal-4C）的C域对具有不同核心表现的ABH-碳水化合物组织血液抗原的结合偏好，并且通过采用包括NMR在内的组合实验方法对其识别特征进行了合理化。固相和血凝试验和分子建模。数据显示，Gal-4C更喜欢A-而不是B-抗原（亲和力是两倍），与N域（Gal-4N）相反，尽管两个域对Type-6演示文稿具有相同的首选项。全长串联重复形式(Gal-4FL)的行为已被进一步检查。ITC和NMR数据表明Gal-4FL中的两个结构域彼此独立地与组织血液抗原结合，他们之间没有交流。在这种情况下，异二聚体建筑不发挥任何主要作用，除了互补的A和B抗原结合偏好。然而,在与含有多价形式的H抗原模拟物作为O抗原的细菌脂多糖（LPS）结合后，揭示了半乳糖凝集素结构的重要性。的确,我们的数据指出接头肽结构域和C结构域的F面是提供Gal-4具有交联多价配体能力的关键元件，超出二聚体的聚糖结合能力。
