Growth Kinetics of Amyloid-like Fibrils Derived from Individual Subunits of Soy β-Conglycinin

• Published in: Journal of agricultural and food chemistry 2011-10, Vol.59 (20), p.11270-11277
• Main Authors: Wang, Jin-Mei, Yang, Xiao-Quan, Yin, Shou-Wei, Yuan, De-Bao, Xia, Ning, Qi, Jun-Ru
• Format: Article
• Language: English
• Subjects: amino acid composition; amyloid; Amyloid - chemistry; Antigens, Plant - chemistry; atomic force microscopy; beta-conglycinin; Biological and medical sciences; Circular Dichroism; dyes; Food Chemistry/Biochemistry; Food industries; Fundamental and applied biological sciences. Psychology; Globulins - chemistry; heat treatment; Hot Temperature; Hydrolysis; Light; light scattering; Microscopy, Atomic Force; polypeptides; Protein Conformation; Protein Structure, Secondary; Protein Subunits - chemistry; Scattering, Radiation; Seed Storage Proteins - chemistry; Soybean Proteins - chemistry
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf202541m

The amyloid-like fibrillation of soy β-conglycinin subunits (α, α′, and β) upon heating (0–20 h) at 85 °C and pH 2.0 was characterized using dynamic light scattering, circular dichroism (CD), binding to amyloid dyes (Thioflavin T and Congo red), and atomic force microscopy. The fibrillation of all three subunits was accompanied by progressive polypeptide hydrolysis. The hydrolysis behaviors, fibrillation kinetics, and morphologies of amyloid-like fibrils considerably varied among α, α′, and β subunits. Faster hydrolysis rates and special fragments were observed for the α and α′ subunits compared to the β subunit. However, the order of the fibrillation rate and capacity to form β-sheets was α′ > β > α, as evidenced by CD and Thioflavin T data. Moreover, sequential growth of twisted screw-structure fibrils, leading to macroscopic fibrils with distinct morphological characteristics, was observed for β-conglycinin and individual subunits. The different fibrillation kinetics and morphologies of α, α′, and β subunits appear to be associated with the differences in the amino acid composition and typical sequence of peptides. Besides, the disruption of ordered structure of fibrils occurred upon further heating (6–20 h) due to extensive hydrolysis. These results would suggest that all subunits are involved in the fibrillation of β-conglycinin, following multiple steps including polypeptide hydrolysis, assembly to amyloid structure, and growth into macroscopic fibrils with a fibril shaving process.