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

Abstract

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 amyloidforming 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.

A Comprehensive Review of Self-Assembled Food Protein-Derived Multicomponent Peptides: From Forming Mechanism and Structural Diversity to Applications

“…For example, Zhang et al demonstrated that acid hydrolysis of 7S and 11S proteins from peas and soybeans could facilitate their self-assembly to form protofibril structures, where the 7S protein hydrolysate self-assembled to form fibers faster than that of the 11S globulin, which is mainly attributed to the higher content of acidic amino acid residues in β-conglycinin. Nevertheless, regions with highly charged and hydrophilic groups were rarely involved in forming protofibrils . Furthermore, it has been demonstrated that enzymatic hydrolysis of sodium caseinate liberated negatively charged peptides that tightly enclosed the surface of the hydrophobic moieties, allowing the peptides to self-assemble into more compact structures …”

“…Nevertheless, regions with highly charged and hydrophilic groups were rarely involved in forming protofibrils. 59 Furthermore, it has been demonstrated that enzymatic hydrolysis of sodium caseinate liberated negatively charged peptides that tightly enclosed the surface of the hydrophobic moieties, allowing the peptides to self-assemble into more compact structures. 22 The hydrophilicity/hydrophobicity and secondary structure elements (such as α-helices or β-sheets) also considerably affect the peptides' self-assembly behavior.…”

In Situ Nanoencapsulation of Curcumin in Soy Protein Isolate Amyloid-like Aggregates for Enhanced Wound Healing

“…This result was in good agreement with that of Zhang and Dee. 23 Since ThT and natural Cur fluorescence emission might interfere, SPIA@Cur formation kinetics were recorded using only the Cur fluorescence signal. The lag time for SPIA@Cur formation was shortened (≈160 min), and the apparent aggregation constant rate was increased significantly.…”

“…3 It is documented that PNF formation from SPI occurs mainly through hydrophobic interactions, while charged and hydrophilic residues have rarely been observed in those regions that participate in PNF formation. 23 In addition to self-assembly and PNF formation, the production of soybean-based protein fibers is now being explored to produce solution-blown spinning fibers with the help of other copolymers. 24 Curcumin (Cur) is the major natural polyphenolic compound of turmeric (Curcuma longa) rhizomes.…”

“…SPI consists of two main reserve globulins: β-conglycinin (7S) and glycinin (11s). , The potential of SPI, β-conglycinin, and glycinin to prepare amyloid-like PNFs, particularly under acidic pH (<2.5) and elevated temperatures (>80 °C) for several hours, has been studied widely. − This is a standard procedure that provides the opportunity for the buried APRs to be exposed and form intermolecular interactions through a series of spontaneous processes, including hydrolysis, unfolding, and assembling into amyloid-like PNFs . It is documented that PNF formation from SPI occurs mainly through hydrophobic interactions, while charged and hydrophilic residues have rarely been observed in those regions that participate in PNF formation . In addition to self-assembly and PNF formation, the production of soybean-based protein fibers is now being explored to produce solution-blown spinning fibers with the help of other copolymers …”