Macromolecular assemblies of complex polysaccharides with galectin-3 and their synergistic effects on function

作者：Tao Zhang, Michelle C. Miller, Yi Zheng, Zhongyu Zhang, Huiting Xue, Dongyang Zhao, Jiyong Su, Kevin H. Mayo, Yifa Zhou, Guihua Tai · 发表于：Biochemical Journal · 年份：2017 · DOI：10.1042/bcj20170143 · 被引用次数：51 · 研究领域：Galectins and Cancer Biology、Glycosylation and Glycoproteins Research、Polysaccharides and Plant Cell Walls

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 KD values of 49 nM, 46 µM, and 138 µM, respectively. 15N-1H 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 13C-1H 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 contri...