Immunoglobulin-E Reactivity and Structural Analysis of Wheat Low-Molecular-Weight Glutenin Subunits and Their Repetitive and Nonrepetitive Halves

The IgE reactivity of the recombinant glutenin subunits P73 and B16, and of their repetitive N-terminal and nonrepetitive C-terminal halves, was analyzed using dot-blot with sera from patients diagnosed with baker's asthma, wheat-dependent exercise-induced anaphylaxis, or allergy to hydrolyzed wheat proteins. The linear epitopes of B16 were identified using the Pepscan method. Except for one common epitope, the IgE binding domains of glutenins differ from those of omega 5-gliadins. Secondary structure content of the proteins was determined using synchrotron radiation circular dichroism (SRCD): while a structures were predominant in all glutenin subunits, fragments, or chimeras, a high IgE reactivity was associated with proteins rich in beta structures. Mixing B16 halves induced conformational interaction, as evidenced by dynamic light scattering and SRCD. IgE reactivity was correlatively increased, as when the halves were associated in the B16 P73 chimera. These results suggest that structural interaction between N- and C-terminal halves may promote epitope presentation.