Location: Produce Safety and Microbiology ResearchTitle: Distinguishing among protein conformations (prion strains) by detecting covalent differences using quantitative mass spectrometry
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/27/2019
Publication Date: 6/21/2019
Citation: Silva, C.J., Erickson-Beltran, M.L. 2019. Distinguishing among protein conformations (prion strains) by detecting covalent differences using quantitative mass spectrometry [abstract]. ASM Microbe 2019, June 20-24, 2019, San Francisco, CA. Poster MBP-19.
Interpretive Summary: N/A
Technical Abstract: A prion (PrPSc) is the simplest of pathogens, a multimer composed of a natively expressed protein in an alternate conformation. It propagates by inducing that natively expressed normal cellular prion protein (PrPC) to adopt the prion conformation. PrPC is a natively expressed monomeric globular protein composed primarily of unstructured and alpha-helical secondary structures. PrPSc is an infectious multimer composed of monomeric 4-rung-beta-solenoids with unstructured loops connecting the rungs of the solenoid. In a beta-solenoid, the side chains of adjacent amino acids alternately project into or out of the beta-solenoid. This means that chemical reactivity of adjacent amino acid side chains can differ dramatically. To further complicate matters, there are different prion strains or conformations, each having a distinct phenotype that is enciphered in the multimeric beta-solenoid architecture. The structural differences that define strains are unknown but may involve beta-solenoids with different starting amino acids, which would put the same amino acid in a different register depending on the strain. Identifying the location of specific amino acids within the beta-solenoid structure would permit the structural definition of a prion strain. Currently, there is no general means of distinguishing between the registers of the beta-solenoid in prions. We used mass spectrometry and proteolytic digestion with either trypsin or chymotrypsin to detect and quantitate covalent differences between the resulting peptides. We used synthetic reagents to covalently modify the epsilon-amino group of lysine and quantitated the oxidation of the thioether of methionine. In this way we were able to detect differences in reactivity of amino acid side chains and to distinguish among prion strains.