|Silva, Christopher - Chris|
Submitted to: Prion
Publication Type: Abstract Only
Publication Acceptance Date: 4/4/2016
Publication Date: 5/10/2016
Citation: Silva, C.J., Erickson-Beltran, M.L., Dynin, I.A. 2016. Using small molecule reagents to help distinguish among prion structural models. Prion 10(Supplement 1). p. S37-S38.
Technical Abstract: The only demonstrated difference between infectious prions (PrPSc) and the isosequential normal cellular prion protein (PrPC) is conformation. The structure of PrPC has been determined by a variety of instrumental techniques. The structure of prions remains uncertain. Recent instrumental analysis has led researchers to conclude that the secondary structure of prions is composed almost entirely of '-sheet. Although this new analysis clarified an element of the secondary structure, it did not define the nature of the '-sheet arrangement. In order to better understand their structure, prions were reacted with a small molecule reagent. 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 the reagent (N-hydroxysuccinimide ester of acetic acid (Ac-NHS)). The extent of lysine acetylation by Ac-NHS was quantitated by mass spectrometry. We determined that each of the lysines in rPrP reacts similarly. However, each of the lysines in the strains reacts differently from the other lysines in a given strain. Furthermore, the lysines in the strains react in a strain-dependent manner. Lysines in the C-terminal region of prions have different strain-dependent reactivity. The results are consistent with one of the two recently proposed models for the structure of a prion. One model proposes that prions are composed of a four-rung '-solenoid structure comprised of four '-sheets that are joined by loops and turns of amino acids. In the '-solenoid structure, amino acids can project toward the center of the solenoid or outward. This could account for the difference in their reactivity. An alternative structure proposes that prions are composed of parallel in-register intermolecular beta-sheets (PIRIBS). In such a structure the amino acid side chains would all be surface exposed and would be expected to react in a similar fashion. Variation in the amino acid composition of the loops and '-sheet structures in the '-solenoid structure is thought to result in different strains of prions.