Characterization of Proteins in Membrane Vesicles from Scrapie-infected Hamster Brain

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Abstract
Previous studies have shown that the scrapie agent is highly membrane-associated. The protein composition of gradient fractions enriched for large membrane vesicles prepared from scrapie-infected and uninfected hamster brain were examined using various methods to extract membrane proteins. Proteins in detergent-extracted membrane vesicles fractionated on CsCl gradients were also examined. No qualitative differences in protein composition were seen comparing scrapie-infected and uninfected samples by 1-dimensional gel electrophoresis. Extraction of proteins from membrane vesicles by phenol, pyridine, perchloric acid or lithium diiodosalicylate also failed to reveal any unique proteins in scrapie-infected hamster brain. Attempts to solubilize hydrophobic proteins (proteolipids) from CsCl gradient fractions into organic solvents were unsuccessful. These findings indicate that any hydrophobic protein associated with the scrapie agent is not a proteolipid, and that the ability of solvents to reduce scrapie infectivity is not a result of extraction of a proteolipid.