The gene for galectin-13 (Gal-13, placental protein 13) is only present in primates, and its low expression level in maternal serum may promote preeclampsia. In the present study, we used pull-down experiments and biolayer interferometry to assess the interaction between Gal-13 and actin. These studies uncovered that human Gal-13 (hGal-13) and Saimiri boliviensis boliviensis (sGal-13) strongly bind to α- and β-/γ-actin, with Ca²⁺ and adenosine triphosphate, significantly enhancing the interactions. This in turn suggests that h/sGal-13 may inhibit myosin-induced contraction when vascular smooth muscle cells undergo polarization. Here, we solved the crystal structure of sGal-13 bound to lactose and found that it exists as a monomer in contrast to hGal-13 which is a dimer. The distribution of sGal-13 in HeLa cells is similar to that of hGal-13, indicating that monomeric Gal-13 is the primary form in cells. Even though sGal-13 binds to actin, hGal-13 ligand-binding site mutants do not influence hGal-13/actin binding, whereas the monomeric mutant C136S/C138S binds to actin more strongly than the wild-type hGal-13. Overall, our study demonstrates that monomeric Gal-13 binds to actin, an interaction that is independent of the galectin canonical ligand-binding site.

中文翻译：

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肌动蛋白与半乳凝素13/胎盘蛋白13的结合独立于半乳凝素经典配体结合位点发生

半乳凝素13（Gal-13，胎盘蛋白13）基因仅存在于灵长类动物中，其在母体血清中的低表达水平可能促进先兆子痫。在本研究中，我们使用下拉实验和生物层干涉仪来评估 Gal-13 和肌动蛋白之间的相互作用。这些研_ ^_和三磷酸腺苷，显着增强相互作用。这反过来表明，当血管平滑肌细胞发生极化时，h/sGal-13 可能会抑制肌球蛋白诱导的收缩。在这里，我们解决了与乳糖结合的 sGal-13 的晶体结构，发现它以单体形式存在，而 hGal-13 是二聚体。sGal-13 在 HeLa 细胞中的分布与 hGal-13 相似，表明单体 Gal-13 是细胞中的主要形式。即使 sGal-13 与肌动蛋白结合，hGal-13 配体结合位点突变体也不影响 hGal-13/肌动蛋白的结合，而单体突变体 C136S/C138S 与肌动蛋白的结合比野生型 hGal-13 更强。总体而言，我们的研究表明单体 Gal-13 与肌动蛋白结合，这是一种独立于半乳凝素经典配体结合位点的相互作用。