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Research Project: Prevention of Obesity Related Metabolic Diseases by Bioactive Components of Food Processing Waste Byproducts and Mitigation of Food Allergies

Location: Healthy Processed Foods Research

Title: Crystal structure of hetero hexameric 11S seed storage protein of hazelnut

item GUO, FENG - Exelixis, Inc
item Zhang, Yuzhu
item HOWARD, ANDREW - Illinois Institute Of Technology
item Xu, Yixiang

Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2024
Publication Date: 4/20/2024
Citation: Guo, F., Zhang, Y., Howard, A., Xu, Y. 2024. Crystal structure of hetero hexameric 11S seed storage protein of hazelnut. Plant Physiology and Biochemistry. 210. Article 108653.

Interpretive Summary: Proteins are essential in human nutrition, and plant-based protein products are becoming increasingly popular. The 11S seed storage protein is one of the most abundant proteins in edible seeds of many plants, especially in pulses and tree nuts. However, the 11S storage proteins from many plants are also food allergens, including peanut allergen Ara h 3, almond allergen Pru du 6, and hazelnut allergen Cor a 9. Thus, information about the 11S proteins’ production, transportation, and accumulation in different parts of the seed and their allergenicity is much needed. This study reports the determination of a hetero hexameric structure of Cor a 9. While more than one isoform of 11S proteins exist in many species, this is the first 11S protein in any species shown to be hetero hexamer. The result may facilitate understanding of the allergenicity of the 11S allergens, improve crop quality, and enhance the future marketability of tree nuts.

Technical Abstract: Edible plant seeds provide a relatively inexpensive source of protein and make up a large part of human nutrition. Plant seeds accumulate storage proteins during seed development. Seed storage proteins act as a reserve of nutrition for seed germination and young sprout growth. However, seed storage proteins may be allergenic, and the prevalence of food allergy has increased rapidly in recent years. The 11S globulins account for a significant number of known major food allergens. They are of interest to the public and the agricultural industry because of food safety concerns and the need for crop enhancement. We sought to determine the crystal structure of Cor a 9, the 11 S storage protein of hazelnut and a food allergen. The structure was refined to 1.92 Å, and the R and Rfree for the refined structure are 17.6% and 22.2%, respectively. The structure of Cor a 9 showed a hetero hexamer of an 11S seed storage protein for the first time. The hexamer was two trimers associated back-to-back. Two long alpha helixes at the C-terminal end of the acidic domain of two of the Cor a 9 isoforms lay along at the cleft of the trimer-trimer interface. These data provided much-needed information about the allergenicity of the 11S seed proteins. The information may also facilitate a better understanding of the folding and transportation of the 11S seed storage protein.