Location: Healthy Processed Foods ResearchTitle: Crystal structure of the Korean pine (Pinus koraiensis) 7S seed storage protein with copper ligands) Author
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2013
Publication Date: 12/11/2013
Publication URL: http://dx.doi.org/10.1021/jf4039887
Citation: Tengchuan, J., Wang, Y., Yu-Wei, C., Fu, T., Kothary, M.H., McHugh, T.H., Zhang, Y. 2013. Crystal structure of the Korean pine (Pinus koraiensis) 7S seed storage protein with copper ligands. Journal of Agricultural and Food Chemistry. 62(1):222-228. DOI: 10.1021/jf4039887. Interpretive Summary: Pine nut allergy cases have been reported, but no pine nut allergen has been identified. Whether pine vicilin is an allergen needs to be determined as they belong to a protein family that includes many known allergens in other foods, including peanut, hazelnut, walnut, cashew, pistachios, etc. Availability of purified pine nut storage proteins and identification and characterization of pine nut allergens will allow a better understanding of the allergenicity of food allergens. This study reported the first structure characterization of putative food allergen in pine nut. This study also found that the pine nut vicilin is a copper protein. This finding may open a new avenue towards understanding the biological function of the protein and the nutrition value of pine nut.
Technical Abstract: The prevalence of food allergy has increased in recent years. Tremendous research progress has been made in the understanding of the pathophysiological mechanisms of allergy and in the identification of food allergens. However, much more research is needed to understand the parameters contributing to the allergenicity of food proteins, including the structural characterization of allergens. Korean pine vicilin is a potential food allergen. We have previously reported the crystallization of Korean pine vicilin purified from raw pine nut. Here we report the isolation of vicilin mRNA and the crystal structure of Korean pine vicilin at 2.40 Angstrom resolution. The overall structure of pine nut vicilin is similar to the structures of other 7S seed storage proteins and consists of an N-terminal domain and a C-terminal domain, each assumes a cupin fold and they are symmetrically related about a pseudo-dyad axis. Three vicilin molecules form a doughnut shaped trimer through head-to-tail association. Structure characterization of Korean pine nut vicilin unexpectedly showed that in its native trimeric state, the vicilin has three copper ligands. Sequence alignments suggested that the copper coordinating residues were conserved in winter squash, sesame, tomato, and several tree nuts, while they were not conserved in a number of legumes including peanut and soybean. Additional studies are needed to assess whether the copper coordinating property of vicilins has a biological function in the relevant plants. The nutritional value of this copper coordinating protein in tree nuts and other edible seeds may be worth further investigations.