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Proteins account for up to ~5% of urban particulate matter, influence the physiochemical properties of atmospheric particles, and play a major role as airborne allergens (Franze, Weller et al. 2003)
Several studies indicated that proteins could be nitrated by NO2 and O3 gas in atmosphere and the nitration took place at the tyrosine residue (Franze, Weller et al. 2005). Moreover, studies have suggested that nitration of proteins alter their allergenicity (Gruijthuijsen, Grieshuber et al. 2006, Untersmayr et al., 2010). To get a better understanding of the nitration procedure, the reaction products and pathways of protein nitration were studied with three different nitration reactants. The recombinant major birch pollen allergen Bet v 1.0101 was nitrated by liquid tetranitromethane (TNM), by liquid peroxynitrite, and by gaseous nitrogen dioxide and ozone (NO2+O3). Each method was applied in multiple steps of titration to obtain proteins with different nitration degrees and to get information about reaction efficiency and site selectivity. The nitration degrees of individual nitrotyrosine residues (NDY) were determined by site-specific quantification with HPLC-MS/MS and compared to the total protein nitration degrees (ND) determined by photometric detection with HPLC-DAD. The observed nitration patterns showed the site selectivity of protein nitration which depended on the nitrating agent, reaction conditions and molecular structure of the protein. These findings suggest different nitration mechanisms as well as interesting insights in nitration pathways occurring under summer smog conditions in the atmosphere (NO2 and O3) or during inflammatory processes in the human body(peroxynitrite). With regard to immunological questions it might be of special interest that the most efficiently nitrated tyrosine residue within the OVA protein (Y107) is part of human as well as murine IgE epitopes of ovalbumin and is also found in a human ovalbumin T cell epitope (Untersmayr, Diesner et al. 2010) The chemical mechanisms and molecular processes that lead to adverse health effects of NO2 and O3 are, however, still poorly understood. We suggest that protein nitration by air pollutants plays a major role in the increase of allergies in the western countries besides nutrition effects and excessive hygiene practices Franze, T., Weller, M. G., Niessner, R. and Pöschl, U. (2003) Analyst, 128(7): 824-831 Franze, T., Weller, M. G., Niessner, R. and Pöschl, U. (2005) Environ. Sci. Technol., 39(6): 1673-1678 Gruijthuijsen, Y. K., Grieshuber, I. et al. (2006) Int. Arch. Allergy Immunol., 141(3): 265-275 Zhang, Y., Hong, Y., Pöschl, U. (2011) Anal. Bioanal. Chem., 399: 459-471 Untersmayr, E., Diesner, S. C. et al. (2010) PLoS ONE 5(12): e14210 |
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