Assistant Professor University of British Columbia Vancouver, British Columbia, Canada
Abstract: Legume seed storage proteins are a sustainable alternative to animal-derived proteins for food and materials applications. The seed storage proteins, which are mostly vicilin and legumin-type globulins, lack sufficient functional properties without extensive modification. One approach is to drive the self-assembly of seed storage proteins into amyloid fibrils by heating at low pH. Under these conditions, the proteins are hydrolyzed into peptides and an unknown sub-set of these assemble into the amyloid fibrils. Our work sought to define the amyloid-forming regions using proteomics and bioinformatics tools, and to characterize their structure-function relationships, using legume proteins (e.g., pea, soy, and lentil) as model systems. Legume seed storage proteins are abundant in amyloid forming regions, typically containing 40-108 amyloid regions of 11-13 aa on average in length, as predicted using bioinformatic tools and confirmed using LC-MS/MS analysis. Fibrillation kinetics can be enhanced by seeding with pre-formed aggregates, decreasing the lag time (from 7 h to 4 h) for lentil fibrils. Lentil protein fibrils formed colourless, translucent gels with a fine networked structure and high mechanical strength (5.2 ± 0.7 kPa) and water holding capacity (87%) at a relatively low protein concentration (6%). The fibril self-assembly mechanism depends strongly on the protein extraction and incubation conditions, and the resulting fibrils show enhanced gelation and rheological properties that make them suitable for use in novel materials. A better understanding of legume protein fibrillation is needed to shed light on recently discovered functional amyloids, and for engineering amyloid-based materials.
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