The molecular mechanism of action of Bevirimat---A prototype HIV-1 maturation inhibitor.

摘要

Due to great plasticity of the Human Immunodeficiency Virus (HIV) type 1, resistance to existing anti-HIV agents is steadily increasing. Therefore, new modalities of treatment are necessary. Bevirimat, a prototype HIV-1 maturation inhibitor, shows high potency in cell culture and is efficacious in HIV infected patients. In contrast to inhibitors that target the active site of the viral protease, bevirimat specifically inhibits a single cleavage event, the final step in the processing of the Gag precursor where p25 (CA-SP1) is cleaved to p24 (CA). In this study, photo-affinity analogs and mass spectrometry were used to map the binding site of bevirimat to Gag within virus-like particles. Immature viral particles were incubated with analogs of bevirimat, exposed to UV light, digested with protease, and analyzed by mass spectrometry. Crosslinked products were identified by their masses and compared to a peptide map of Gag to identify the location of crosslinking. Consistent with previous biochemical data on the effect of bevirimat on Gag processing and with genetic data from resistance mutations, bevirimat analogs were found to crosslink to sequences near the CA-SP1 cleavage site, which was predicted by NMR and mutational studies to contain α-helical character. Unexpectedly, a second interaction site was identified within the Major Homology Region (MHR). Extensive prior genetic evidence suggests the MHR is a critical assembly region. This is the first demonstration of a direct interaction between the maturation inhibitor, bevirimat, and its target, Gag. Information gained from this study will aid future design of maturation inhibitors and reveal the mechanisms by which the virus may become resistant to this class of drug.