TOXI 120 |
| As a post-translational modification, the hydrolytic deamidation of internal asparaginyl and glutaminyl protein residues leads to significant changes in protein function. We have previously reported on a non-hydrolytic mechanism of deamidation that can occur in the presence of aerobic nitric oxide (NO). Here we show that such nitrosative deamidation can slow and even reverse aggregation of a model poly(glutamine/asparagine) peptide, the amyloidogenic GNNQQNY domain of the yeast prion protein Sup35. When the initially monomeric peptide was dissolved at a concentration of 1.2 mM in water at 37 oC, abundant aggregates consisting primarily of thick, elongated, needle-like structures were quickly visible by transmission electron micrography (TEM), and the course of aggregation as followed by dynamic light scattering (DLS) converted essentially all the ~1-nm monomer to ~100-nm fibrils within 25 min. When the procedure was repeated in the presence of the NO donor compound DEA/NO [Et2NN(O)=NONa, 7.5 mM], fibril formation was reduced, no aggregates being seen by TEM until 50 min, with DLS showing the virtual absence of 100-nm particles over 6 h. When the preformed fibrils were exposed to 8.5 mM DEA/NO for 24 h, the initially needle-like fibrils were strikingly changed in size, shape, number, and general appearance, as revealed by TEM. The possible significance of nitrosative peptide deamidation with respect to protein folding and function in health and disease will be discussed. |
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Poster Session and Awards
6:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- 204 A/B, Poster
Division of Chemical Toxicology |