The scrapie agent (prion) resisted inactivation by procedures that modify nucleic acids but was inactivated by procedures that modify proteins, distinguishing it from viroids and viruses.
The scrapie agent's resistance to nucleic acid-modifying procedures and sensitivity to protein-modifying procedures distinguishes it from viroids and supports the concept of the 'prion'.
Viroids are small "naked" infectious RNA molecules that are pathogens of higher plants. The potato spindle tuber viroid (PSTV) is composed of a covalently closed circular RNA molecule containing 359 ribonucleotides. The properties of PSTV were compared with those of the scrapie agent, which causes a degenerative neurological disease in animals. PSTV was inactivated by ribonuclease digestion, psoralen photoadduct formation, Zn2+ -catalyzed hydrolysis, and chemical modification with NH2OH. The scrapie agent resisted inactivation by these procedures, which modify nucleic acids. The scrapie agent was inactivated by proteinase K and trypsin digestion, chemical modification with diethylpyrocarbonate, and by exposure to phenol, NaDodSO4, KSCN, or urea. PSTV resisted inactivation by these procedures, which modify proteins. Earlier evidence suggested that the scrapie agent is smaller than PSTV. Its small size seems to preclude the presence of a genome coding for the protein(s) of a putative capsid. The properties of the scrapie agent distinguish it from both viroids and viruses and have prompted the introduction of the term "prion" to denote a small proteinaceous infectious particle that resists inactivation by procedures that modify nucleic acids.
Diener et al. (Wed,) conducted a other in Degenerative neurological disease (scrapie). Scrapie agent (prion) vs. Potato spindle tuber viroid (PSTV) was evaluated on Inactivation by various chemical and enzymatic procedures. The scrapie agent (prion) resisted inactivation by procedures that modify nucleic acids but was inactivated by procedures that modify proteins, distinguishing it from viroids and viruses.