title: Small-Angle X-ray Scattering Study of Protein Complexes with Tea Polyphenols.
abstract: 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.
authors.affiliation: Key Laboratory of Synthetic Rubber & Laboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry , Changchun 130022, People's Republic of China.
authors.forename: Ce
authors.initials: C
authors.lastname: Shi
authors.affiliation: 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.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Tang
authors.affiliation: Department of Food Science, Rutgers University , 65 Dudley Road, New Brunswick, New Jersey 08901, United States.
authors.forename: Jie
authors.initials: J
authors.lastname: Xiao
authors.affiliation: Key Laboratory of Synthetic Rubber & Laboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry , Changchun 130022, People's Republic of China.
authors.forename: Fengchao
authors.initials: F
authors.lastname: Cui
authors.affiliation: Key Laboratory of Synthetic Rubber & Laboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry , Changchun 130022, People's Republic of China.
authors.forename: Kecheng
authors.initials: K
authors.lastname: Yang
authors.affiliation: Department of Food Science, Rutgers University , 65 Dudley Road, New Brunswick, New Jersey 08901, United States.
authors.forename: Ji
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Food Science, Rutgers University , 65 Dudley Road, New Brunswick, New Jersey 08901, United States.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: Department of Food Science, Rutgers University , 65 Dudley Road, New Brunswick, New Jersey 08901, United States.
authors.forename: Qingrong
authors.identifier: http://orcid.org/0000-0001-8637-0229
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Key Laboratory of Synthetic Rubber & Laboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry , Changchun 130022, People's Republic of China.
authors.forename: Yunqi
authors.identifier: http://orcid.org/0000-0002-5190-3037
authors.initials: Y
authors.lastname: Li
mesh_terms: D028241:Camellia sinensis / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*; D059808:Polyphenols / Q000737:chemistry*; D011485:Protein Binding; D053838:Scattering, Small Angle; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013662:Tea / Q000737:chemistry; D014357:Trypsin / Q000737:chemistry*
chemical_list: D010936:Plant Extracts; D059808:Polyphenols; D013662:Tea; D012710:Serum Albumin, Bovine; D014357:Trypsin
keywords: aggregation; conformation; protein; solution small-angle X-ray scattering; tea polyphenol