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J Agric Food Chem. 2017 Jan 18;65(2):454-462. doi: 10.1021/acs.jafc.6b04387. Epub 2017 Jan 5.

Purification and Characterization of a Black Walnut (Juglans nigra) Allergen, Jug n 4.

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Western Regional Research Center, Pacific West Area, Agricultural Research Service, U.S. Department of Agriculture , 800 Buchanan Street, Albany, California 94710, United States.
School of Food Science and Technology, Jiangnan University , 214122 Wuxi, China.
College of Chemistry and Environmental Engineering, Shenzhen University , Shenzhen 518060, China.
Division of Pediatric Immunology, Allergy, and Rheumatology, Department of Pediatrics, Stanford University School of Medicine , 269 Campus Drive, Stanford, California 94305, United States.
Southwest Research Center, Division of Plant Sciences, University of Missouri , 14548 Highway H, Mt Vernon, Missouri 65712, United States.


Tree nuts as a group cause a significant number of fatal anaphylactic reactions to foods. Walnuts (Juglans spp.) are one of the leading causes of allergic reactions to tree nuts in the U.S. and Japan. The purpose of this study was to purify and characterize potential food allergens from black walnut. Here, we report the isolation of the black walnuts allergen Jug n 4 (an 11S globulin) by ammonium sulfate precipitation, hydrophobic interaction, and size exclusion chromatography. Reducing SDS-PAGE analysis indicated that purified Jug n 4 consists of three major bands. N-Terminal sequencing data of these bands indicated that they were the results of a post-transcriptional protease cleavage of the mature protein at a site that consists of a known conserved protease recognition motif, NGXEET. Western blot experiments revealed that 32% of the sera from 25 patients with double-blind, placebo-controlled clinical walnut allergy contained IgE antibodies that recognized Jug n 4, indicating that it is a walnut allergen. Identifying this and additional allergens may facilitate the understanding of the allergenicity of seed storage proteins in tree nuts and their cross-reactivity.


Jug n 4; dbpcfc; food allergen; post-transcriptional modification; storage protein

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