A recombinant ribonuclease H domain of HIV-1 reverse transcriptase that is enzymatically active.

We report here a human immunodeficiency virus type 1 (HIV-1) recombinant ribonuclease H (RNase H) domain engineered to contain an N-terminal tag for its isolation by affinity chromatography. The purified protein is active in hydrolyzing RNA-DNA hybrids in two separate in vitro assay systems. In light of recent reports of similar HIV-1 RNase H domains which were enzymatically inactive (Becerra, S.

Superoxide radical and superoxide dismutases: threat and defense.

An enzymic flux of O2- and H2O2 caused strand breaks in the supercoiled covalently closed circular Col El plasmid. Subnanomolar levels of superoxide levels of superoxide dismutase or of catalase prevented this attack on DNA, signifying that both O2- and H2O2 were required. Benzoate, mannitol or histidine, which do not scavenge O2- or H2O2, also protected the DNA suggesting that the proximate attacking species had a reactivity comparable to that of the hydroxyl radical.