Biosynthesis and analysis of a genetically engineered HIV-1 reverse transcriptase/endonuclease polyprotein in Escherichia coli.

Elimination of the protease domain from the polymerase open reading frame (pol) of the human immunodeficiency virus type 1 (HIV-1) leads, in Escherichia coli, to synthesis and accumulation of a non-processed 98-kDa reverse transcriptase/endonuclease (RT/ENDO) polyprotein. A partially purified preparation of this reverse RT/ENDO polyprotein displays little or no RT activity. Introduction of the pol protease domain as a separate transcriptional unit on the same plasmid restores the processing program, generating correctly sized RT and ENDO polypeptides. Concomitant with restoration of processing is the reappearance of RT activity. These results suggest that for HIV-1 RT to be active, it must be matured from the pol polyprotein.