Location: Produce Safety and Microbiology ResearchTitle: Oxidizing methionine to map a prion's surface and reveal conformational differences
Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 12/20/2021
Publication Date: 3/23/2022
Citation: Silva, C.J., Erickson-Beltran, M.L. 2022. Oxidizing methionine to map a prion's surface and reveal conformational differences [Abstract]. Abstracts of the American Chemical Society. Spring 2022 Meeting. March 23, 2022. Abstract number: 365591. https://doi.org/10.1021/scimeetings.2c00113.
Technical Abstract: A prion’s pathogenic character is enciphered in its conformation. Additionally, conformation defines the chemical environments of its component amino acids and their reactivity. Mammalian cells express methionine sulfoxide-reducing enzymes (Msr A and B) to maintain surface exposed methionines in their naturally reduced state. Natively expressed mammalian proteins are largely devoid of methionine oxidation and, therefore, possess little background oxidation. Quantifying the oxidation of a prion’s methionines resulting from experimental chemical oxidation permits researchers to identify surface exposed methionines and, thereby, reveal conformation-dependent information. Oxidizing a prion’s methionines does not substantially reduce its infectivity, implying that a prion’s structure is not perturbed when its methionines are oxidized. We identified a set of methionine-containing peptides derived from the tryptic, chymotryptic or tryptic/chymotryptic digestion of recombinant hamster PrP (rPrP). We developed a multiple reaction monitoring (MRM) based method of quantifying the extent of the methionine oxidation in those peptides. We used our MRM method to quantify the extent of the methionine oxidation in rPrP and the Sc237 strain of hamster-adapted scrapie after experimental oxidation. Conformation-dependent differences in susceptibility of methionines to oxidation was observed. Such information can be used to distinguish among prion strains and to guide modelers in developing computation-based prion structures.