Impact of lipid binding on the tertiary structure and allergenic potential of Jug r 3, the non-specific lipid transfer protein from walnut

Abstract

Plant non-specific lipid transfer proteins type 1 (nsLTP1) are small basic proteins with a hydrophobic cavity able to host a number of different ligands: i.e. fatty acids, fatty acyl-CoA, phospholipids, glycolipids, and hydroxylated fatty acids. However, ligand binding specificity differs among nsLTPs. Within this protein family, Jug r 3 from walnut has been identified as a major allergen. So far, data on the structural characterization of Jug r 3 and its lipid binding capacity are lacking. We report the results from a fluorescence-based ligand-binding assay and ligand-based NMR experiments, to study the binding interactions between Jug r 3 and the 18-carbon monounsaturated oleic acid. Furthermore, protein-based NMR experiments were employed to detect the oleate binding site of Jug r 3. The NMR data were used to dock the oleate molecule into the structural model of Jug r 3. Finally, the impact of the interaction on the allergenic potential of Jug r 3 was investigated by IgE ELISA with 6 sera from walnut allergic patients. Our data corroborate the hypothesis of direct impact of food-derived matrix on the IgE reactivity of nsLTPs.

Structural characterization and in vitro lipid binding studies of non-specific lipid transfer protein 1 (nsLTP1) from fennel (Foeniculum vulgare) seeds

“…5TVI is selected as the best template based on BLASTp result; it is 59.34% identical and 74% similar to fennel nsLTP1 with 100% query coverage and e-value of 3E−33. The homology modeling, therefore, indicated that the structure of fennel nsLTP1 has four α-helices: H1 (4-20), H2 (26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38), H3 (42-57) and H4 (64-74); a long C-terminal tail (75-91); and three short loops at the positions of (21-25), (37-41), (58)(59)(60)(61)(62)(63) residues. The study from the crystal structure of 5TVI depicted that these helices are engaged in the form of a hydrophobic cavity, where the overall structure is stabilized by the presence of four disulfide bonds that exist between cysteine (4-51), (14-28), and ) that are also retained by fennel nsLTP1 structure 16 .…”

“…7). The presence of one cis-double bond in FAs with a chain length of C18 (as in linoleic acid) has a higher affinity for the protein as it enforces the FA to a curved shape for easier accommodation in the binding site 23,[56][57][58] . Moreover, the binding assay revealed an initial increase in the percentage of fennel nsLTP1-TNS fluorescence at the lower concentration of displacing FAs, followed by a decrease in the intensity at higher FA concentration (Fig.…”

Impact of Different Lipid Ligands on the Stability and IgE-Binding Capacity of the Lentil Allergen Len c 3

“…Finally, a study of IgE-reactivity in the cases of the intact or preincubated with lipid ligands rLen c 3 was performed. Recently, it has been shown that preincubation of the peach allergen Pru p 3 [ 28 ], the walnut Jug r 3 [ 29 ], the apple Mal d 3, and the hazelnut Cor a 8 [ 30 ] with OLE increased IgE-binding capacity of the allergens. It has been assumed that changes in protein structures upon complex formation with this ligand could lead to an exposure of additional IgE epitopes.…”

Identification and Physicochemical Characterization of a New Allergen from Ascaris lumbricoides

“…The implications of these observations will serve as a base for future studies and to further analyze and get experimental structural data on the atomic level by X-ray crystallography or NMR spectroscopy and confirm residues involved in metal binding and its stoichiometry, as well as, to study possible effects of one metal ligand on the binding of the other. In addition, since protein ligands can influence allergenicity by affecting allergen tertiary structure and biochemical attributes [35][36][37] the study of structural modifications induced by ligands might help to analyze possible relationships between allergen structure and allergenicity. rAsc l 5 binds IgE with high frequency in Ascaris-sensitized individuals as evaluated in different populations: 44% in FRAAT and 58% in SC.…”