Diener T O, McKinley M P, Prusiner S B
Proc Natl Acad Sci U S A. 1982 Sep;79(17):5220-4. doi: 10.1073/pnas.79.17.5220.
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.
类病毒是小型“裸露”的传染性RNA分子，是高等植物的病原体。马铃薯纺锤块茎类病毒（PSTV）由一个共价闭合的环状RNA分子组成，包含359个核糖核苷酸。将PSTV的特性与羊瘙痒病病原体的特性进行了比较，羊瘙痒病病原体可在动物中引起退行性神经疾病。PSTV可通过核糖核酸酶消化、补骨脂素光加合物形成、Zn2+催化水解以及用NH2OH进行化学修饰而失活。羊瘙痒病病原体对这些修饰核酸的程序具有抗性。羊瘙痒病病原体可通过蛋白酶K和胰蛋白酶消化、用焦碳酸二乙酯进行化学修饰以及暴露于苯酚、十二烷基硫酸钠、硫氰酸钾或尿素而失活。PSTV对这些修饰蛋白质的程序具有抗性。早期证据表明，羊瘙痒病病原体比PSTV小。其小尺寸似乎排除了存在编码假定衣壳蛋白的基因组。羊瘙痒病病原体的特性使其有别于类病毒和病毒，并促使引入“朊病毒”一词来表示一种小型蛋白质传染性颗粒，该颗粒对修饰核酸的程序具有抗性。
