Foot and mouth disease virus II. Endoribonuclease activity within purified virions

Highly purified FMDV virions have a ribonuclease located within the viral particles. The enzyme is an endonuclease; it degrades the genomic RNA in situ upon prolonged incubation (20–25 hr) of the virions at 37°C. The enzyme acts gradually and produces intermediate RNA fragments which always have the same size distribution. Based on the results suggesting that other molecules such as Sarkosyl and pancreatic ribonuclease are not able to penetrate inside intact virions, even after prolonged incubation at 37°C, it was postulated that the enzyme is incorporated into the virion during the viral morphogenesis. However, the origin of this enzyme is at present unknown.