Lactose Binding to Galectin-1 Modulates Structural Dynamics, Increases Conformational Entropy, and Occurs with Apparent Negative Cooperativity
Lactose Binding to Galectin-1 Modulates Structural Dynamics, Increases Conformational Entropy, and Occurs with Apparent Negative Cooperativity
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DOI：
10.1016/j.jmb.2010.02.033
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发表时间：
2010-04-16
影响因子：
5.6
通讯作者：
Mayo, Kevin H.
中科院分区：
文献类型：
--
作者：
Nesmelova, Irina V.;Ermakova, Elena;Mayo, Kevin H.
Galectins是一个具有保守的碳水化合物识别结构域的凝集素家族，它与β-半乳糖苷相互作用。半乳糖凝集素-1(Galectin-1，GAL-1)通过与细胞表面糖结合，参与细胞的黏附和迁移过程，是肿瘤血管生成的重要调节因子。在这里，我们使用异核核磁共振波谱和分子模拟来研究乳糖与GAL-1的结合，并推导出乳糖结合和非结合状态下GAL-1的溶液核磁共振结构。结构分析表明，在非结合状态下，乳糖结合部位周围的β-链和环更加开放和动态，折叠在结合的乳糖分子周围，抑制该部位的内部运动，并增加整个蛋白质其他地方的运动，以熵方式贡献结合自由能。CD数据支持乳糖结合状态下整体更开放结构的观点。对异核单量子相干滴定结合数据的分析表明，乳糖以负协同作用结合了GAL-1二聚体的两个碳水化合物识别结构域，其中第一个乳糖分子结合得更强(K-1=21+/-6×10(3)M-1)，第二个分子结合更强(K-2=4+/-2×10(3)M-1)。用顺序结合模型拟合的等温量热数据呈现出类似的情况，得到K-1=20+/-10×10(3)M-1和K-2=1.67+/-0.07×10(3)M-1。分子动力学模拟提供了对半负载乳糖状态的结构动力学的洞察，并结合核磁共振数据表明，乳糖在一个位点上结合通过β-三明治传递信号，并循环到第二个结合位点。总体而言，我们的结果为GAL-1结构-功能关系和蛋白质-碳水化合物的相互作用提供了新的见解。(C)2010年由爱思唯尔有限公司出版。
Galectins are a family of lectins with a conserved carbohydrate recognition domain that interacts with beta-galactosides. By binding cell surface glycoconjugates, galectin-1 (gal-1) is involved in cell adhesion and migration processes and is an important regulator of tumor angiogenesis. Here, we used heteronuclear NMR spectroscopy and molecular modeling to investigate lactose binding to gal-1 and to derive solution NMR structures of gal-1 in the lactose-bound and unbound states. Structure analysis shows that the beta-strands and loops around the lactose binding site, which are more open and dynamic in the unbound state, fold in around the bound lactose molecule, dampening internal motions at that site and increasing motions elsewhere throughout the protein to contribute entropically to the binding free energy. CD data support the view of an overall more open structure in the lactose-bound state. Analysis of heteronuclear single quantum coherence titration binding data indicates that lactose binds the two carbohydrate recognition domains of the gal-1 dimer with negative cooperativity, in that the first lactose molecule binds more strongly (K-1 = 21 +/- 6 x 10(3) M-1) than the second (K-2= 4 +/- 2 x 10(3) M-1). Isothermal calorimetry data fit using a sequential binding model present a similar picture, yielding K-1 = 20 +/- 10 x 10(3) M-1 and K-2 = 1.67 +/- 0.07 x 10(3) M-1. Molecular dynamics simulations provide insight into structural dynamics of the half-loaded lactose state and, together with NMR data, suggest that lactose binding at one site transmits a signal through the beta-sandwich and loops to the second binding site. Overall, our results provide new insight into gal-1 structure-function relationships and to protein-carbohydrate interactions in general. (C) 2010 Published by Elsevier Ltd.