Purification and further characterization of an RNA-dependent DNA polymerase from the allantoic fluid of leukosis-virus-free chicken eggs.

The purification of an RNA-dependent DNA polymerase from the allantoic fluid of uninfected, embryonated chicken eggs is described in detail. Comparison to the polymerase of avian myeloblastosis virus shows that the two enzymes are different with respect to ion concentrations for optimal reaction, response to increasing concentrations of substrate, thermal stability and protection from thermal inactivation by viral RNA. It is concluded that the enzymes compared to each other are different proteins, which must have been coded by different genes. The RNA-dependent DNA polymerase in the allantoic fluid, therefore, does not derive from the partial or complete expression of the endogenous virus genome of the normal chicken cell or from infection by exogenous viruses.