title: Crystal structure at 1.9-A resolution of human immunodeficiency virus (HIV) II protease complexed with L-735,524, an orally bioavailable inhibitor of the HIV proteases.
abstract: L-735,524 is a potent, orally bioavailable inhibitor of human immunodeficiency virus (HIV) protease currently in a Phase II clinical trial. We report here the three-dimensional structure of L-735,524 complexed to HIV-2 protease at 1.9-A resolution, as well as the structure of the native HIV-2 protease at 2.5-A resolution. The structure of HIV-2 protease is found to be essentially identical to that of HIV-1 protease. In the crystal lattice of the HIV-2 protease complexed with L-735,524, the inhibitor is chelated to the active site of the homodimeric enzyme in one orientation. This feature allows an unambiguous assignment of protein-ligand interactions from the electron density map. Both Fourier and difference Fourier maps reveal clearly the closure of the flap domains of the protease upon L-735,524 binding. Specific interactions between the enzyme and the inhibitor include the hydroxy group of the hydroxyaminopentane amide moiety of L-735,524 ligating to the carboxyl groups of the essential Asp-25 and Asp-25' enzymic residues and the amide oxygens of the inhibitor hydrogen bonding to the backbone amide nitrogen of Ile-50 and Ile-50' via an intervening water molecule. A second bridging water molecule is found between the amide nitrogen N2 of L-735,524 and the carboxyl oxygen of Asp-29'. Although other hydrogen bonds also add to binding, an equally significant contribution to affinity arises from hydrophobic interactions between the protease and the inhibitor throughout the pseudo-symmetric S1/S1', S2/S2', and S3/S3' regions of the enzyme. Except for its pyridine ring, all lipophilic moieties (t-butyl, indanyl, benzyl, and piperidyl) of L-735,524 are rigidly defined in the active site.
authors.affiliation: Department of Biological Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486.
authors.forename: Z
authors.initials: Z
authors.lastname: Chen
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: E
authors.initials: E
authors.lastname: Chen
authors.forename: D L
authors.initials: DL
authors.lastname: Hall
authors.forename: P L
authors.initials: PL
authors.lastname: Darke
authors.forename: C
authors.initials: C
authors.lastname: Culberson
authors.forename: J A
authors.initials: JA
authors.lastname: Shafer
authors.forename: L C
authors.initials: LC
authors.lastname: Kuo
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004351:Drug Resistance; D016333:HIV Protease / Q000737:chemistry; D017320:HIV Protease Inhibitors / Q000378:metabolism*; D019469:Indinavir; D011725:Pyridines / Q000378:metabolism*
chemical_list: D017320:HIV Protease Inhibitors; D011725:Pyridines; D019469:Indinavir; D016282:Aspartic Acid Endopeptidases; D016333:HIV Protease; C065184:p16 protease, Human immunodeficiency virus 2