Crystal structure determination and analysis of 11S coconut allergen: Cocosin

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

Edible plant seeds provide a relatively inexpensive source of protein and make up a large part of nutrients for humans. Plant seeds accumulate storage proteins during seed development. Seed storage proteins act as a reserve of nutrition for seed germination and seedling 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 22.5%, 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 one of the Cor a 9 isoforms lay at the trimer-trimer interface's groove. 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 11S seed storage proteins.

Food Allergens of Plant Origin

This review presents an update on the physical, chemical, and biological properties of food allergens in plant sources, focusing on the few protein families that contribute to multiple food allergens from different species and protein families recently found to contain food allergens. The structures and structural components of the food allergens in the allergen families may provide further directions for discovering new food allergens. Answers as to what makes some food proteins allergens are still elusive. Factors to be considered in mitigating food allergens include the abundance of the protein in a food, the property of short stretches of the sequence of the protein that may constitute linear IgE binding epitopes, the structural properties of the protein, its stability to heat and digestion, the food matrix the protein is in, and the antimicrobial activity to the microbial flora of the human gastrointestinal tract. Additionally, recent data suggest that widely used techniques for mapping linear IgE binding epitopes need to be improved by incorporating positive controls, and methodologies for mapping conformational IgE binding epitopes need to be developed.

Self-Assembly of Hausmannite Mn3O4 Triangular Structures on Cocosin Protein Scaffolds for High Energy Density Symmetric Supercapacitor Application

Recent advances in using biological scaffolds for nanoparticle synthesis have proven to be useful for preparing various nanostructures with uniform shape and size. Proteins are significant scaffolds for generating various nanostructures partly because of the presence of many functional groups to recognize different chemistries. In this endeavor, cocosin protein, an 11S allergen, is prepared from coconut fruit and employed as a potential scaffold for synthesizing Mn₃O₄ materials. The interaction between protein and manganese ions is studied in detail through isothermal calorimetric titration. At increased scaffold availability, the Mn₃O₄ material adopts the exact hexamer structure of the cocosin protein. The electrochemical supercapacitive properties of the cocosin-Mn₃O₄ material are found to have a high specific capacitance of 751.3 F g^-1 at 1 A g^-1 with cyclic stability (92% of capacitance retention after 5000 CV cycles) in a three-electrode configuration. The Mn₃O₄//Mn₃O₄ symmetric supercapacitor device delivers a specific capacitance of 203.8 F g^-1 at 1 A g^-1 and an outstanding energy and power density of 91.7 W h kg^-1 and 899.5 W kg^-1, respectively. These results show that cocosin-Mn₃O₄ could be considered a suitable electrode for energy storage applications. Moreover, the cocosin protein to be utilized as a novel scaffold in protein-nanomaterial chemistry could be useful for protein-assisted inorganic nanostructure synthesis in the future.