title: Conformation of inhibitor-free HIV-1 protease derived from NMR spectroscopy in a weakly oriented solution.
abstract: Flexibility of the glycine-rich flaps is known to be essential for catalytic activity of the HIV-1 protease, but their exact conformations at the different stages of the enzymatic pathway remain subject to much debate. Although hundreds of crystal structures of protease-inhibitor complexes have been solved, only about a dozen inhibitor-free protease structures have been reported. These latter structures reveal a large diversity of flap conformations, ranging from closed to semi-open to wide open. To evaluate the average structure in solution, we measured residual dipolar couplings (RDCs) and compared these to values calculated for crystal structures representative of the closed, semi-open, and wide-open states. The RDC data clearly indicate that the inhibitor-free protease, on average, adopts a closed conformation in solution that is very similar to the inhibitor-bound state. By contrast, a highly drug-resistant protease mutant, PR20, adopts the wide-open flap conformation.
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892 (USA). julien.roche@nih.gov.
authors.forename: Julien
authors.initials: J
authors.lastname: Roche
authors.forename: John M
authors.initials: JM
authors.lastname: Louis
authors.forename: Ad
authors.initials: A
authors.lastname: Bax
mesh_terms: D016333:HIV Protease / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D012996:Solutions / Q000737:chemistry
chemical_list: D012996:Solutions; D016333:HIV Protease; C514803:p16 protease, Human immunodeficiency virus 1
keywords: HIV protease; active sites; flap dynamics; liquid crystal NMR spectroscopy; residual dipolar coupling