A 12amino acid peptide, residues 33-44 of the large subunit (QGLRGEEMEEMV), was strongly recognised by sera from 5 individuals out of 20, moderately by 6/20, weakly by 4/20 and not recognised at all by 5/20. Mutational analysis showed that RGEE (residues 36-39 of the large subunit) were necessary and E (residue 42 of the large subunit) important for recognition. A mixture of peptides did not inhibit all Jug r 1 specific IgE binding, demonstrating that conformational epitopes are also recognised (Robotham et al. 2002 [693]).
Allergen stability: Process, chemical, enzymatic
Jug r 1 belongs to the 2S family of seed storage albumin proteins. As these have four disulfide bridges, they tend to be relatively resistant to denaturation and proteolysis.
Nature of main cross-reacting proteins:
Jug r 1 exhibits a 46.1% identity with the Brazil nut (Bertholletia excelsa) methionine-rich 2S albumin seed storage protein allergen precursor, Ber e 1.
Allergen properties & biological function:
Jug r 1 is one of the 2S albumin storage proteins in walnut. It is an heterodimer composed of a large and a small subunit joined by disulfide bridges. Post-translational processing of the 142 amino acids long precursor results in the two subunits. Such processing is similar to that which takes place in castor bean, cottonseed, mustard seed, and Brazil nut 2S seed storage protein allergens.
Allergen purification:
Recombinant Jug r 1 has been expressed and purified both via a fusion protein and as a His-tagged protein (Teuber et al. 1998 [206]; Robotham et al. 2002 [693]).
Other biochemical information:
Robotham et al. (2002) [693] identify the small subunit as NPRRRGEGCREQIQRQQNLNHCQYYLR (26 residues) and the large subunit as RQHFRQCCQQLSQMDEQCQCEGLRQVVRRQQQQQGLRGEEMEEMVQSARDLPNECGISSQRCEIR (64 residues).
Jug r 1 appears to be an important walnut food allergen; 12 of 16 sera from patients allergic to walnuts showed IgE binding to the 2S albumin seed storage protein precursor presented as a fusion protein (Teuber et al. 1998 [206]), which removed reaction to walnut extracts at 14, 10 and 4 kDa.
References (2)
Robotham JM, Teuber SS, Sathe SK, Roux KH.
Linear IgE epitope mapping of the English walnut (Juglans regia)major food allergen, Jug r 1.
J Allergy Clin Immunol. 109(1):143-149. 2002
PUBMED ID:
11799381
Teuber SS, Dandekar AM, Peterson WR, Sellers CL
Cloning and sequencing of a gene encoding a 2S albumin seed storage protein precursor from English walnut (Juglans regia), a major food allergen.
J Allergy Clin Immunol 101:807-814. 1998
PUBMED ID:
9648708
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