Ultrastructural Cytochemistry Of Enzymes Associated With Murine Leukemia Viruses .I. Adenosine Triphosphatase

Ultrastructural cytochemistry of plasma‐virus pellets from mice injected with Rauscher or Moloney virus showed a phosphatase activity specific for adenosine triphosphate and diphosphate, and for inosine triphosphate and diphosphate. This enzymatic activity was localized at the viral envelope and was associated with only part of the virus population. Moloney virus showed a smaller proportion of active virions than Rauscher virus. The adenosine triphosphatase activity associated with the murine leukemia viruses was far less pronounced than that associated with avian myeloblastosis virus. The origin of this enzymatic activity has not been clarified. Since the envelope of the budding viruses reflects some of the properties of the budding cell membrane, the adenosine triphosphatase of the blood‐forming organs was extensively investigated. Most of the virus‐replicating cells were adenosine triphosphatase‐negative in these organs. The viral enzyme might be adsorbed at the surface of the virus by electrostatic forces.