Conformational changes of Mal d 2, a thaumatin-like apple allergen, induced by food processing
2009
Marzban, Gorji | Herndl, Anita | Pietrozotto, Sara | Banerjee, Srijib | Obinger, Christian | Maghuly, Fatemeh | Hahn, Rainer | Boscia, Donato | Katinger, Hermann | Laimer, Margit
Mal d 2, a thaumatin-like protein from apple was previously described to react to almost 75% of the apple allergic patient sera. Based on the molecular structure of this protein, the present study focused on the conformational stability of Mal d 2 in relation to in vitro IgE-binding under different physico-chemical conditions and proteolysis. The structural integrity of Mal d 2 was monitored using SDS-PAGE, Western blotting using polyclonal antibodies and human sera, fluorescence spectrometry and circular dichroism. Results confirmed the stability of Mal d 2. However, Mal d 2 was reactive to human serum IgEs mainly after reduction of disulphide bridges fixing the α-helical domain II. Contrary to previous assumptions, the current findings suggest that the allergenic epitopes of Mal d 2 are hidden inside the protein structure and none of the rigorous conditions applied in industrial juice processing or digestive proteolysis enhance or reduce the binding to IgE molecules.
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