The Inhibitory Effects of a Rhamnogalacturonan I (RG-I) Domain from Ginseng Pectin on Galectin-3 and Its Structure-Activity Relationship
The Inhibitory Effects of a Rhamnogalacturonan I (RG-I) Domain from Ginseng Pectin on Galectin-3 and Its Structure-Activity Relationship
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人参果胶鼠李糖半乳糖醛酸 I (RG-I) 结构域对 Galectin-3 的抑制作用及其构效关系
DOI：
10.1074/jbc.m113.482315
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发表时间：
2013-11-22
影响因子：
4.8
通讯作者：
Zhou, Yifa
中科院分区：
文献类型：
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作者：
Gao, Xiaoge;Zhi, Yuan;Zhou, Yifa
果胶已被证明可以抑制半乳糖凝集素-3的作用，半乳糖凝集素-3是一种与癌症进展相关的半乳糖苷结合蛋白。参与这一活动的果胶的结构特征尚不清楚。研究了不同人参果胶对半乳糖凝集素-3作用的影响。鼠李糖半乳糖酸i丰富的果胶片段，RG-I-4，有效抑制半乳糖凝集素3介导的血凝，癌细胞粘附和同型聚集，以及半乳糖凝集素3与t细胞的结合。RG-I-4特异结合半乳糖凝集素-3的碳水化合物识别结构域，解离常数为22.2 nm，通过表面等离子体共振分析确定。通过各种酶和化学方法修饰RG-I-4的结构，并进行活性测试，研究了RG-I-4的构效关系。结果表明(a)半乳聚糖侧链对RG-I-4的活性至关重要，而阿拉伯糖侧链则根据其在RG-I-4分子中的位置正或负调节活性。(b)半乳链的活性与其长度成正比，直到4个Gal残基，此后基本不变。(c) RG-I-4中大部分的半乳糖侧链较短，活性较低。(d) RG-I-4的高活性源于这些侧链的协同作用。(e)分子的主干对RG-I-4的活性非常重要，可能是通过维持整个分子的结构构象。(f)分离的骨架可以结合半乳糖凝集素-3，而半乳糖凝集素对乳糖处理不敏感。新发现的侧链和主链在调节RG-I-4活性中发挥着不同的作用，这对于生产高活性的基于果胶的半乳糖凝集素-3抑制剂是有价值的。
Pectin has been shown to inhibit the actions of galectin-3, a -galactoside-binding protein associated with cancer progression. The structural features of pectin involved in this activity remain unclear. We investigated the effects of different ginseng pectins on galectin-3 action. The rhamnogalacturonan I-rich pectin fragment, RG-I-4, potently inhibited galectin-3-mediated hemagglutination, cancer cell adhesion and homotypic aggregation, and binding of galectin-3 to T-cells. RG-I-4 specifically bound to the carbohydrate recognition domain of galectin-3 with a dissociation constant of 22.2 nm, which was determined by surface plasmon resonance analysis. The structure-activity relationship of RG-I-4 was investigated by modifying the structure through various enzymatic and chemical methods followed by activity tests. The results showed that (a) galactan side chains were essential to the activity of RG-I-4, whereas arabinan side chains positively or negatively regulated the activity depending on their location within the RG-I-4 molecule. (b) The activity of galactan chain was proportional to its length up to 4 Gal residues and largely unchanged thereafter. (c) The majority of galactan side chains in RG-I-4 were short with low activities. (d) The high activity of RG-I-4 resulted from the cooperative action of these side chains. (e) The backbone of the molecule was very important to RG-I-4 activity, possibly by maintaining a structural conformation of the whole molecule. (f) The isolated backbone could bind galectin-3, which was insensitive to lactose treatment. The novel discovery that the side chains and backbone play distinct roles in regulating RG-I-4 activity is valuable for producing highly active pectin-based galectin-3 inhibitors.