Galectin-3 (Gal-3), a β-galactoside binding lectin, has been implicated in a plethora of pathological disorders including fibrosis, inflammation, cancer, and metabolic diseases. TD139 - a thio-digalactoside inhibitor developed by Galecto Biotech as a potential therapeutic for idiopathic pulmonary fibrosis, is the most advanced small-molecule galectin-3 inhibitor in clinical studies. It binds to human Gal-3 with high affinity but has lower affinity towards mouse and rat homologs, which is also manifested in the differential inhibition of Gal-3 function. Using biophysical methods and high resolution X-ray co-crystal structures of TD139 and Gal-3 proteins, we demonstrate that a single amino acid change corresponding to A146 in human Gal-3 is sufficient for the observed reduction in the binding affinity of TD139 in rodents. Site-directed mutagenesis of A146V (in human Gal-3) & V160A (in mouse Gal-3) was sufficient to interchange the affinities, mainly by affecting the off rates of the inhibitor binding. Additionally, molecular dynamics simulations of both wild type and mutant structures revealed the sustained favorable non-covalent interactions between the fluorophenyl ring and the active site A146 (human Gal-3 and mouse V160A) that corroborate the finding from biophysical studies. Current findings have ramifications in the context of optimization of drug candidates against Gal-3.

中文翻译：

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TD139与Galectin-3结合亲和力种间差异的分子机制

Galectin-3 (Gal-3) 是一种 β-半乳糖苷结合凝集素，与多种病理疾病有关，包括纤维化、炎症、癌症和代谢性疾病。TD139是Galecto Biotech开发的硫代双半乳糖苷抑制剂，作为特发性肺纤维化的潜在治疗药物，是临床研究中最先进的小分子半乳糖凝集素3抑制剂。它以高亲和力与人 Gal-3 结合，但对小鼠和大鼠同系物的亲和力较低，这也表现在对 Gal-3 功能的差异抑制。使用 TD139 和 Gal-3 蛋白的生物物理学方法和高分辨率 X 射线共晶结构，我们证明了对应于人 Gal-3 中 A146 的单个氨基酸变化足以观察到 TD139 在啮齿动物。A146V（在人 Gal-3 中）和 V160A（在小鼠 Gal-3 中）的定点诱变足以互换亲和力，主要是通过影响抑制剂结合的解离率。此外，野生型和突变型结构的分子动力学模拟揭示了氟苯环与活性位点 A146（人 Gal-3 和小鼠 V160A）之间持续有利的非共价相互作用，这证实了生物物理学研究的发现。目前的研究结果在优化针对 Gal-3 的候选药物方面产生了影响。野生型和突变型结构的分子动力学模拟揭示了氟苯环和活性位点 A146（人 Gal-3 和小鼠 V160A）之间持续有利的非共价相互作用，这证实了生物物理学研究的发现。目前的研究结果在优化针对 Gal-3 的候选药物方面产生了影响。野生型和突变型结构的分子动力学模拟揭示了氟苯环和活性位点 A146（人 Gal-3 和小鼠 V160A）之间持续有利的非共价相互作用，这证实了生物物理学研究的发现。目前的研究结果在优化针对 Gal-3 的候选药物方面产生了影响。