Sequence-specific 1H, 13C and 15N resonance assignments of Ara h 6, an allergenic 2S albumin from peanut.

Abstract

In many countries peanuts contribute significantlyto the total dietary protein and peanuts or peanutbyproducts are widely used as supplements in manydifferent types of foods. Despite the eminent nutri-tional properties of this legume, peanuts can causesevere, type I hypersensitivity reactions (Bochner andLichtenstein, 1991). Peanut allergy is a significanthealth problem because of the prevalence and sever-ity of the reaction and is more often associated withfatal-induced anaphylaxis than any other food allergy(Yunginger et al., 1988; Sampson et al., 1992). Due tothe life-threateningcharacterofthis reactionthe devel-opment of therapeutic and prophylactic strategies areof extreme importance. For a detailed understandingof the molecular mechanisms of food-induced aller-gies and for the development of therapeutic strategies,knowledgeof high-resolutionthree-dimensionalstruc-tures of allergenic proteins is essential. Although sev-eral different major and minor peanut allergens havebeen isolated, only very few structural data for aller-genic peanut proteins exist. The 2S albumin Ara h 6(Kleber-Janke et al., 1999) represents one of three2S albumin type allergens among at least six aller-genic components in peanuts and shows a sequenceidentity of 58,5% to the well investigated major al-lergen Ara h 2 (Burks et al., 1992). 2S albuminsare storage proteins widely distributed in plant seeds.These proteins include several disulfide bridges, thecysteines forming a conserved pattern (Shewry et al.,2001). In addition to their role as nitrogen and sul-fur donor that has been proposed from their aminoacid composition, activities as antifungal, serine pro-tease inhibitor, and calmodulin antagonists have beenascribed for several 2S albumins (Shewryet al., 2001).Moreover, the 2S albumin family is an important classof food allergens of well recognized clinical import-ance. Several allergenic 2S albumins were identifiedin different seeds and nuts such as mustard, sesame,Brazil nut, walnut, and peanut (Pastorello et al., 2001).This interesting protein group contains many highlypotent allergens and many studies explored the aller-genic character of this proteins using immunologicalas well as mutational methods. Nevertheless, only onestructural study of a 2S albumin, that of napin BnIbfrom rape seeds (Rico et al., 1996), was carried out sofar. This BnIb structure only presents the global foldof the protein due to experimental restrictions arisingfrom the heterogeneity of the protein sample isolatedfrom rapeseed (Rico et al., 1996). Recently we repor-ted a recombinant strategy for the efficient large-scalepreparation of properly folded and disulfide bridgedAra h 2 for structural studies (Lehmann et al., 2003).Exploiting