Characterization of reverse transcriptase from feline immunodeficiency virus

Reverse transcriptase has been purified from feline immunodeficiency virus (FIV) by DEAE-cellulose and phosphocellulose chromatography. The purified enzyme consists of a single protein with a M_r of 67,000. When proteolysis is not minimized during purification, a fragment of M_r 54,000 is also observed. This is similar to the reverse transcriptase from human immunodeficiency virus type 1 (HIV), which consists of a polypeptide of M_r 66,000; when proteolysis is not minimized during purification, a fragment of M_r 51,000 is also observed. In direct comparisons, the FIV reverse transcriptase is very similar to the HIV reverse transcriptase in template specificity and requirements for Mg²⁺. In contrast to these similarities, the FIV and HIV reverse transcriptases are substantially different in primary sequence, as determined by peptide mapping.