Ligand induced galectin-3 protein self-association.
Ligand induced galectin-3 protein self-association.
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DOI：
10.1074/jbc.c112.358002
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发表时间：
2012-06-22
期刊：
影响因子：
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通讯作者：
Leffler H
中科院分区：
文献类型：
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作者：
Lepur A;Salomonsson E;Nilsson UJ;Leffler H
背景：一种lectectin-3功能是结合糖蛋白并交叉链接。
结果：糖蛋白与其相关聚糖的数量相比，糖蛋白接合更多的Galectin-3碳水化合物结合位点。
结论：配体诱导的一个lectectin-3与另一个Galectin-3的结合以先前未知的方式形成低聚物。
意义：这与以前的模型不同，并提供了一个新框架来解释Galectin-3的生物学效应。
乳糖素3的许多功能需要其碳水化合物识别位点与糖蛋白的聚糖的结合，从而导致交联被认为是由其N端非碳水化合物结合结构域介导的。 ASIALOFETUIN（ASF），使用荧光各向异性测定法测量溶液中的游离半乳糖素识别位点的浓度。即使在高乳糖素-3浓度下保持较低，表明由于大约9个已知的基于Glycan的结合位点，因此，每个ASF分子的结合位点比预期的比预期更多。通过碳水化合物识别位点结合到另一个Galectin-3分子，我们将其命名为Cy-C的自我关联。拟议的模型（type-N），其中galectin-3分子通过N末端结构域相互结合，并且所有碳水化合物识别位点都可以用于结合两种类型的自相结合。和动态光散射。野生型（〜1μm）也诱导了较弱的c型自我关联，而galectin-3缺少其N末端域，但正如预期的那样，既没有降水量。 - 即使后者产生高浓度的lectectin-3（> 〜50μm）的沉淀，含有聚糖诱导的型C型自我关联，这与已发表的结果一致，并且可能是由于N型自我关联所致。
Background: One galectin-3 function is to bind glycoproteins and cross-link them. Results: A glycoprotein engaged many more galectin-3 carbohydrate-binding sites than its number of relevant glycans. Conclusion: The ligand induced binding of one galectin-3 to another galectin-3 to form oligomers in a previously unrecognized way. Significance: This differs from previous models and provides a new framework to interpret biological effects of galectin-3. Many functions of galectin-3 entail binding of its carbohydrate recognition site to glycans of a glycoprotein, resulting in cross-linking thought to be mediated by its N-terminal noncarbohydrate-binding domain. Here we studied interaction of galectin-3 with the model glycoprotein asialofetuin (ASF), using a fluorescence anisotropy assay to measure the concentration of free galectin carbohydrate recognition sites in solution. Surprisingly, in the presence of ASF, this remained low even at high galectin-3 concentrations, showing that many more galectin-3 molecules were engaged than expected due to the about nine known glycan-based binding sites per ASF molecule. This suggests that after ASF-induced nucleation, galectin-3 associates with itself by the carbohydrate recognition site binding to another galectin-3 molecule, possibly forming oligomers. We named this type-C self-association to distinguish it from the previously proposed models (type-N) where galectin-3 molecules bind to each other through the N-terminal domain, and all carbohydrate recognition sites are available for binding glycans. Both types of self-association can result in precipitates, as measured here by turbidimetry and dynamic light scattering. Type-C self-association and precipitation occurred even with a galectin-3 mutant (R186S) that bound poorly to ASF but required much higher concentration (∼50 μm) as compared with wild type (∼1 μm). ASF also induced weaker type-C self-association of galectin-3 lacking its N-terminal domains, but as expected, no precipitation. Neither a monovalent nor a divalent N-acetyl-d-lactosamine-containing glycan induced type-C self-association, even if the latter gave precipitates with high concentrations of galectin-3 (>∼50 μm) in agreement with published results and perhaps due to type-N self-association.