title: Transient HIV-1 Gag-protease interactions revealed by paramagnetic NMR suggest origins of compensatory drug resistance mutations.
abstract: Cleavage of the group-specific antigen (Gag) polyprotein by HIV-1 protease represents the critical first step in the conversion of immature noninfectious viral particles to mature infectious virions. Selective pressure exerted by HIV-1 protease inhibitors, a mainstay of current anti-HIV-1 therapies, results in the accumulation of drug resistance mutations in both protease and Gag. Surprisingly, a large number of these mutations (known as secondary or compensatory mutations) occur outside the active site of protease or the cleavage sites of Gag (located within intrinsically disordered linkers connecting the globular domains of Gag to one another), suggesting that transient encounter complexes involving the globular domains of Gag may play a role in guiding and facilitating access of the protease to the Gag cleavage sites. Here, using large fragments of Gag, as well as catalytically inactive and active variants of protease, we probe the nature of such rare encounter complexes using intermolecular paramagnetic relaxation enhancement, a highly sensitive technique for detecting sparsely populated states. We show that Gag-protease encounter complexes are primarily mediated by interactions between protease and the globular domains of Gag and that the sites of transient interactions are correlated with surface exposed regions that exhibit a high propensity to mutate in the presence of HIV-1 protease inhibitors.
authors: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
authors: Lalit
authors: L
authors: Deshmukh
authors: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
authors: John M
authors: JM
authors: Louis
authors: Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
authors: Rodolfo
authors: R
authors: Ghirlando
authors: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892; mariusc@mail.nih.gov.
authors: G Marius
authors: GM
authors: Clore
mesh_terms: D020134:Catalytic Domain; D024882:Drug Resistance, Viral / Q000235:genetics; D015658:HIV Infections / Q000188:drug therapy / Q000821:virology; D016333:HIV Protease / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017320:HIV Protease Inhibitors / Q000494:pharmacology; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding / Q000187:drug effects; D000072417:Protein Domains; D017433:Protein Structure, Secondary; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D017320:HIV Protease Inhibitors; D054301:gag Gene Products, Human Immunodeficiency Virus; D016333:HIV Protease; C514803:p16 protease, Human immunodeficiency virus 1
keywords: HIV-1 Gag; HIV-1 protease; drug resistance mutations; invisible states; paramagnetic relaxation enhancement