Morphology, Formation Kinetics and Core Composition of Pea and Soy 7S and 11S Globulin Amyloid Fibrils

Legume seed storage proteins can be induced to form amyloid fibrils upon heating at low pH, which could improve their functionality for use in food and materials. However, the amyloidogenic regions of legume proteins are largely unknown. Here, we used LC-MS/MS to determine the amyloid core regions of fibrils formed by enriched pea and soy 7S and 11S globulins at pH 2, 80 °C, and characterized their hydrolysis, assembly kinetics, and morphology. A lag phase was absent from the fibrillation kinetics of pea and soy 7S globulins, while 11S globulins and crude extracts displayed a similar lag time. Pea and soy protein fibrils differed in morphology, with most pea fibrils being straight and soy fibrils being worm-like. Pea and soy globulins were abundant in amyloid-forming peptides, with over 100 unique fibril-core peptides from pea 7S and around 50 unique fibril-core peptides identified from pea 11S, soy 7S, and soy 11S globulins. Amyloidogenic regions derive predominantly from the homologous core region of 7S globulins and the basic subunit of 11S globulins. Overall, pea and soy 7S and 11S globulins are rich in amyloidogenic regions. This study will help understand their fibrillation mechanism and engineer protein fibrils with specific structures and functionality.