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Title: Covalent surface modification of prions: a mass spectrometry-based means of detecting distinctive structural features of prion strains

item Silva, Christopher - Chris
item Erickson-Beltran, Melissa
item DYNIN, IRINA - Former ARS Employee

Submitted to: Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2016
Publication Date: 1/19/2016
Publication URL:
Citation: Silva, C.J., Erickson-Beltran, M.L., Dynin, I.C. 2016. Covalent surface modification of prions: a mass spectrometry-based means of detecting distinctive structural features of prion strains. Biochemistry. 55:894-902.

Interpretive Summary: Prions are infectious proteins. The only difference between a prion and the natively expressed normal cellular prion protein is their conformation or shape. Five different prion strains, each with a different shape, were reacted with a synthetic reagent. It was designed to react with a particular amino acid (lysine) in the prion, in a shape-dependent manner. The reagent forms a distinct chemical bond (acetylation). The extent of the reaction for the five strains was monitored by a mass spectrometer. Each strain reacted differently with the reagent. These differences in reactivity can be used to tell strains apart. These differences in reactivity offer experimental support for a recently proposed model of the shape of prions.

Technical Abstract: Prions (PrPSc) are molecular pathogens that are able to convert the isosequential normal cellular prion protein (PrPC) into a prion. The only demonstrated differences between PrPC and PrPSc is conformational, they are isoforms. A given host can be infected by more than one kind or strain of prion. Five strains of hamster-adapted scrapie (Sc237 (=263K), drowsy, 139H, 22AH, and 22CH) and recombinant PrP were reacted with five different concentrations (0, 1, 5, 10, or 20 mM) of reagent (N-hydroxysuccinimide ester of acetic acid (Ac-NHS)) that acetylates lysines. The extent of lysine acetylation was quantitated by mass spectrometry. The lysines in rPrP react similarly. The lysines in the strains react differently from one another in a given strain and react differently when strains are compared. Lysines in the C-terminal region of prions have different strain-dependent reactivity. The results are consistent with a recently proposed model for the structure of a prion. This model proposes that prions are composed of a ß-solenoid structure comprised of four ß-sheets that are joined by loops and turns of amino acids. Variation in the amino acid composition of the loops and ß-sheet structures is thought to result in different strains of prions.