HIV-2 protease is inactivated after oxidation at the dimer interface and activity can be partly restored with methionine sulphoxide reductase

Human immunodeficiency viruses encode a homodimeric protease that is essent ial for the production of infectious virus. Previous studies have shown tha t HIV-1 protease is susceptible to oxidative inactivation at the dimer inte rface at Cys-95, a process that can be reversed both chemically and enzymic ally, Here we demonstrate a related yet distinct mechanism of reversible in activation of the HIV-2 protease. Exposure of the HIV-2 protease to H2O2 re sulted in conversion of the two methionine residues (Met-76 and Met-95) to methionine sulphoxide as determined by amino acid analysis and mass spectro metry. This oxidation completely inactivated protease activity. However, th e activity could be restored (up to 40%) after exposure of the oxidized pro tease to methionine sulphoxide reductase, This treatment resulted in the re duction of methionine sulphoxide 95 but not methionine sulphoxide 76 to met hionine, as determined by peptide mapping/mass spectrometry. We also found that exposure of immature HIV-2 particles to H2O2 led to the inhibition of polyprotein processing in maturing virus particles comparable to that demon strated for HIV-1 particles. Thus oxidative inactivation of the HIV proteas e in vitro and in maturing viral particles is not restricted to the type 1 proteases, These studies indicate that two distinct retroviral proteases ar e susceptible to inactivation after a very minor modification at residue 95 of the dimer interface and suggest that the dimer interface might be a via ble target for the development of novel protease inhibitors.