P39, a Novel Soybean Protein Allergen, Belongs to a Plant-Specific Protein Family and Is Present in Protein Storage Vacuoles

Ping Xiang†, Lisa M. Baird§, Rudolf Jung#, Michael G. Zeece, John Markwell and Gautam Sarath*
British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada, Biology Department, University of San Diego, San Diego, California 92110, Pioneer-Hybrid International, Johnston, Iowa 50131, Department of Food Science and Technology, University of Nebraska, Lincoln, Nebraska 68583-0919, Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68583-0718, and Grain, Forage and Bioenergy Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Lincoln, Nebraska 68583-0737
J. Agric. Food Chem., 2008, 56 (6), pp 2266–2272
DOI: 10.1021/jf073292x
Publication Date (Web): February 20, 2008
Copyright © 2008 American Chemical Society
†

British Columbia Cancer Agency.

,
§

University of San Diego.

,
#

Pioneer-Hybrid International.

,

Department of Food Science and Technology, University of Nebraska.

,

Department of Biochemistry, University of Nebraska.

,
* Author to whom correspondence should be addressed [e-mail Gautam.Sarath@ars.usda.gov; telephone (402) 472-4204 ; fax (402)472-4020].
,

U.S. Department of Agriculture.

Abstract

Soybean lecithins are seeing increasing use in industry as an emulsifier and food additive. They are also a growing source of human food allergies, which arise principally from the proteins fractionating with the lecithin fraction during manufacture. A previous study (Gu, X.; Beardslee, T.; Zeece, M.; Sarath, G.; Markwwell, J. Int Arch. Allergy Immunol. 2001, 126, 218−225) identified several allergenic proteins in soybean lecithins and a soybean IgE-binding protein termed P39 was discovered. However, very little was known about this protein except that it was coded by the soybean genome. This paper investigates key biological and immunological properties of this potential soybean lecithin allergen. P39 is encoded by a multigene family in soybeans and in several other higher plants. The soybean P39-1 protein and its essentially indistinguishable homologue, P39-2, have been cloned and studied. These proteins and their homologues belong to a family of plant-specific proteins of unknown function. In soybeans, P39-1 is seed specific, and its transcript levels are highest in developing seeds and decline during seed maturation. In contrast, P39 protein was detectable only in the fully mature, dry seed. Subcellular fractionation revealed that P39 protein was strongly associated with oil bodies; however, immunolocalization indicated P39 was distributed in the matrix of the protein storage vacuoles, suggesting that association with oil bodies was an artifact arising from the extraction procedure. By the use of recombinant techniques it has also been documented that IgE-binding epitopes are present on several different portions of the P39-1 polypeptide.

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History

  • Published In Issue March 26, 2008
  • Article ASAPFebruary 20, 2008
  • Received: November 09, 2007
    Accepted: December 19, 2007
    Revised: December 18, 2007

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