Galectin-10 (Gal-10) which forms Charcot-Leyden crystals in vivo, is crucial to regulating lymph cell function. Here, we solved the crystal structures of Gal-10 and eight variants at resolutions of 1.55–2.00 Å. Structural analysis and size exclusion chromatography demonstrated that Gal-10 dimerizes with a novel global shape that is different from that of other prototype galectins (e.g., Gal-1, -2 and -7). In the Gal-10 dimer, Glu33 from one subunit modifies the carbohydrate-binding site of another, essentially inhibiting disaccharide binding. Nevertheless, glycerol (and possibly other small hydroxylated molecules) can interact with residues at the ligand binding site, with His53 being the most crucial for binding. Alanine substitution of the conserved Trp residue (Trp72) that is crucial to saccharide binding in other galectins, actually leads to enhanced erythrocyte agglutination, suggesting that Trp72 negatively regulates Gal-10 ligand binding. Overall, our crystallographic and biochemical results provide insight into Gal-10 ligand binding specificity.

中文翻译：

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Galectin-10：一种新的原型半乳糖凝集素二聚体结构类型及其对糖配体结合的影响

Galectin-10（Gal-10）在体内形成Charcot-Leyden晶体，对调节淋巴细胞功能至关重要。在这里，我们以1.55–2.00Å的分辨率解析了Gal-10的晶体结构和8个变体。结构分析和尺寸排阻色谱法表明，Gal-10以不同于其他原型半乳糖凝集素（例如Gal-1，-2和-7）的新型整体形状二聚。在Gal-10二聚体中，来自一个亚基的Glu33修饰了另一个亚基的碳水化合物结合位点，基本上抑制了二糖的结合。但是，甘油（可能还有其他小的羟基化分子）可以与配体结合位点上的残基相互作用，His53对于结合至关重要。丙氨酸取代保守的Trp残基（Trp72），这对于其他半乳糖凝集素中的糖结合至关重要，实际上导致增强的红细胞凝集，表明Trp72负调控Gal-10配体结合。总体而言，我们的晶体学和生化结果可深入了解Gal-10配体的结合特异性。