Zhang Tao, Miller Michelle C, Zheng Yi, Zhang Zhongyu, Xue Huiting, Zhao Dongyang, Su Jiyong, Mayo Kevin H, Zhou Yifa, Tai Guihua
Jilin Province Key Laboratory for Chemistry and Biology of Natural Drugs in Changbai Mountain, School of Life Sciences, Northeast Normal University, Changchun 130024, PR China.
Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN 55455, U.S.A.
Biochem J. 2017 Nov 9;474(22):3849-3868. doi: 10.1042/BCJ20170143.
Although pectin-derived polysaccharides can antagonize galectin function in various pathological disorders, the nature of their binding interactions needs to be better defined for developing them as drugs. Moreover, given their relatively large size and complexity, pectin-derived polysaccharides are also useful as model systems to assess inter-polysaccharide and protein-polysaccharide interactions. Here, we investigated interactions between galectin-3 (Gal-3) and pectin-derived polysaccharides: a rhamnogalacturonan (RG) and two homogalacturonans (HGs). BioLayer Interferometry and fluorescence-linked immunosorbent assays indicate that these polysaccharides bind Gal-3 with macroscopic or apparent values of 49 nM, 46 µM, and 138 µM, respectively. N-H heteronuclear single quantum coherence (HSQC) NMR studies reveal that these polysaccharides interact primarily with the F-face of the Gal-3 carbohydrate recognition domain. Even though their binding to Gal-3 does not inhibit Gal-3-mediated T-cell apoptosis and only weakly attenuates hemagglutination, their combination in specific proportions increases activity synergistically along with avidity for Gal-3. This suggests that RG and HG polysaccharides act in concert, a proposal supported by polysaccharide particle size measurements and C-H HSQC data. Our model has HG interacting with RG to promote increased avidity of RG for Gal-3, likely by exposing additional lectin-binding sites on the RG. Overall, the present study contributes to our understanding of how complex HG and RG polysaccharides interact with Gal-3.
尽管果胶衍生的多糖可在各种病理疾病中拮抗半乳糖凝集素的功能，但为了将其开发成药物，需要更明确地界定它们结合相互作用的性质。此外，鉴于其相对较大的尺寸和复杂性，果胶衍生的多糖也可用作评估多糖间相互作用以及蛋白质 - 多糖相互作用的模型系统。在此，我们研究了半乳糖凝集素 -3（Gal-3）与果胶衍生的多糖之间的相互作用：一种鼠李糖半乳糖醛酸聚糖（RG）和两种同型半乳糖醛酸聚糖（HG）。生物层干涉术和荧光连锁免疫吸附测定表明，这些多糖与Gal-3结合的宏观或表观解离常数分别为49 nM、46 μM和138 μM。N - H异核单量子相干（HSQC）核磁共振研究表明，这些多糖主要与Gal-3碳水化合物识别结构域的F面相互作用。尽管它们与Gal-3的结合并不抑制Gal-3介导的T细胞凋亡，且仅微弱减弱血细胞凝集，但它们按特定比例组合可协同增加活性以及与Gal-3的亲和力。这表明RG和HG多糖协同发挥作用，多糖粒度测量和C - H HSQC数据支持了这一观点。我们的模型显示HG与RG相互作用，可能通过暴露RG上额外的凝集素结合位点来促进RG对Gal-3亲和力的增加。总体而言，本研究有助于我们理解复杂的HG和RG多糖如何与Gal-3相互作用。
