Kinetic stability of 11s globulin storage protein in tree nuts: implications for allergenicity
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Authors
Franquiz Santos, Christian, Alexander
Issue Date
2024-05
Type
Electronic thesis
Thesis
Thesis
Language
en_US
Keywords
Chemistry
Alternative Title
Abstract
Kinetically stable proteins (KSPs) are proteins that display a high activation energy for unfolding that traps them in a specific conformation, which allows them to resist degradation. Kinetic stability (KS) allows proteins to play important biological roles, as it helps them resist harsh in vivo conditions, allows them to persist in high abundance for long periods of time, it protects them from aggregation, and may regulate the timing of physiological events. Because KSPs are known to be more resistant to proteolytic degradation they have been linked to food intolerance and allergy. One of the essential non-animal protein sources present in most human diets involves legumes and nuts, and among them the main proteins are seed storage proteins (SSPs). One of the most abundant SSPs is the 11S globulin, an important nutrient storage protein involved in plant growth and germination, that is a major allergen. Since it is well-known that many allergenic proteins are hyperstable and degradation-resistant, this novel study probes the KS of the 11S globulin SSPs from the nine most common tree nuts (TN), one of the main allergenic food groups in the world. Furthermore, the study explores a possible correlation between KS and allergenicity within this important protein family. This study involved the grinding and preparation of whole-nut, crude protein extracts followed by analysis through various gel electrophoresis methods that allow the assessment of KS without the need for protein purification. We used polyacrylamide gel electrophoresis (PAGE) to assess the target 11S globulins’ resistance to denaturation by the strong detergent sodium dodecyl sulfate (SDS) and the weak detergent sodium lauroyl sarcosinate (SAR) as a proxy for different levels of KS. These two detergents are combined at different ratios in a method known as SDS-SAR-PAGE co-mixing to visualize the denaturation transition of proteins of interest as they unfold due to the increasing SDS:SAR ratio. The resulting KS assessments were then used to categorize each TN 11S globulin into groups of high, medium, or low KS. Finally, the experimental data was correlated with allergy prevalence statistics found in the scientific literature for each TN. Specifically, we used studies which analyzed individuals allergic to each individual TN, and determined which of them recognized the 11S globulin allergen. These studies made it possible to determine the intrinsic and relevant importance of the 11S globulin in eliciting allergic reactions across patients allergic to each TN, when compared to other SSPs. By correlating the extent of experimentally determined KS with allergy prevalence statistics for the different TN, we observed an encouraging correlation between the two factors, suggesting KS may have a significant role in developing TN allergy. The results from this study suggest that within the protein inherent factors that are known to determine the allergenic potential in food, the stability of a protein, specifically its KS, is an important factor that could contribute towards their allergenicity. Hence, further quantifying the KS of 11S globulins in different species could help probe the broader relevance of the results from this study. Furthermore, expanding research efforts focused on KS and its role in allergy across other proteins beyond SSPs could be an important step forward in advancing protein allergy research at the molecular level.
Finally, the implications of these results not only encompass the possible role of protein KS in allergenicity and protein digestibility, but also its possible role in seed germination, survival, and vigor. 11S globulins are known to perform a variety of germination and biodefense roles that may ensure survival. Our results suggest that 11S globulins may have developed varied levels of KS to maintain these non-storage roles. A promising future research direction stemming from the efforts and results of this study include exploring the link between protein KS and different plant biodefense and survival roles.
Description
May2024
School of Science
School of Science
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY