Purification and kinetic characterization of equine infectious anemia virus reverse transcriptase.

The reverse transcriptase of Equine Infectious Anemia Virus (EIAV) was partially purified from virus particles and appeared to be a heterodimer with subunit molecular masses of 70 kdal and 59 kdal. The polymerase activity of this enzyme had an absolute requirement for a divalent cation, preferring Mg++ over Mn++. Addition of a monovalent cation to the reaction mixture enhanced, but was not required for enzyme activity. Kinetically, the reverse transcriptase of EIAV is similar to the reverse transcriptase of Human Imunodeficiency Virus Type 1 (HIV-1). Both enzymes have similar Km values for 2'-deoxynucleoside-5'-triphosphates on the synthetic template/primers tested, both exhibit substrate inhibition, and both are inhibited to similar extents by most nucleoside-triphosphate analogs. The results of this study suggest that the reverse transcriptase of EIAV may be a good model for studying structure/function relationships of retroviral reverse transcriptases.