Shi Ce, Tang Haifeng, Xiao Jie, Cui Fengchao, Yang Kecheng, Li Ji, Zhao Qin, Huang Qingrong, Li Yunqi
Key Laboratory of Synthetic Rubber & Laboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry , Changchun 130022, People's Republic of China.
School of Life Science, Jilin University , Changchun 130012, People's Republic of China.
J Agric Food Chem. 2017 Jan 25;65(3):656-665. doi: 10.1021/acs.jafc.6b04630. Epub 2017 Jan 11.
Exploration of the structure of protein complexes, especially the change in conformation and aggregation behavior of proteins upon ligand binding, is crucial to clarify their bioactivities at the molecular level. We applied solution small-angle X-ray scattering (SAXS) to study the complex structure of bovine serum albumin (BSA) and trypsin binding with tea polyphenols, that is, catechin and epigallocatechin gallate (EGCG). We found that tea polyphenols can steadily promote the aggregation of proteins and protein complexes through their bridging effect. The numbers of proteins in the complexes and in the aggregates of complexes are extracted from SAXS intensity profiles, and their dependences as a function of the molar ratio of polyphenol to protein are discussed. EGCG has stronger capability than catechin to promote complex formation and further aggregation, and the aggregates of complexes have a denser core with a relatively smooth surface. The aggregates induced by catechin are loosely packed with a rough surface. BSA shows higher stability than trypsin in the formation of complex with a well-folded conformation. The synergistic unfolding of trypsin results in larger aggregates in the mixtures with more tea polyphenols. The binding affinity and number of tea polyphenols bound to each protein are further determined using fluorescence spectroscopy. The structure of protein complexes explored in this work is referable in the preparation of protein complex-based particles and the understanding of polyphenol-induced formation and further aggregation of protein complexes.
探索蛋白质复合物的结构，尤其是蛋白质在配体结合后构象和聚集行为的变化，对于在分子水平上阐明其生物活性至关重要。我们应用溶液小角X射线散射（SAXS）来研究牛血清白蛋白（BSA）和胰蛋白酶与茶多酚（即儿茶素和表没食子儿茶素没食子酸酯（EGCG））结合的复合物结构。我们发现茶多酚可以通过其桥连作用稳定地促进蛋白质和蛋白质复合物的聚集。从SAXS强度分布中提取复合物和复合物聚集体中的蛋白质数量，并讨论它们作为多酚与蛋白质摩尔比的函数的依赖性。EGCG促进复合物形成和进一步聚集的能力比儿茶素更强，并且复合物的聚集体具有更致密的核心和相对光滑的表面。儿茶素诱导的聚集体堆积松散，表面粗糙。在形成具有良好折叠构象的复合物时，BSA比胰蛋白酶表现出更高的稳定性。胰蛋白酶的协同解折叠导致在含有更多茶多酚的混合物中形成更大的聚集体。使用荧光光谱进一步确定茶多酚与每种蛋白质的结合亲和力和结合数量。这项工作中探索的蛋白质复合物结构对于基于蛋白质复合物的颗粒的制备以及理解多酚诱导的蛋白质复合物的形成和进一步聚集具有参考价值。
