title: Polyoxometalate HIV-1 protease inhibitors. A new mode of protease inhibition.
abstract: Nb-containing polyoxometalates (POMs) of the Wells-Dawson class inhibit HIV-1 protease (HIV-1P) by a new mode based on kinetics, binding, and molecular modeling studies. Reaction of alpha(1)-K(9)Li[P(2)W(17)O(61)] or alpha(2)-K(10)[P(2)W(17)O(61)] with aqueous H(2)O(2) solutions of K(7)H[Nb(6)O(19)] followed by treatment with HCl and KCl and then crystallization affords the complexes alpha(1)-K(7)[P(2)W(17)(NbO(2))O(61)] (alpha(1)()1) and alpha(2)-K(7)[P(2)W(17)(NbO(2))O(61)] (alpha(2)()1) in 63 and 86% isolated yields, respectively. Thermolysis of the crude peroxoniobium compounds (72-96 h in refluxing H(2)O) prior to treatment with KCl converts the peroxoniobium compounds to the corresponding polyoxometalates (POMs), alpha(1)-K(7)[P(2)W(17)NbO(62)] (alpha(1)()2) and alpha(2)-K(7)[P(2)W(17)NbO(62)] (alpha(2)()2), in moderate yields (66 and 52%, respectively). The identity and high purity of all four compounds were confirmed by (31)P NMR and (183)W NMR. The acid-induced dimerization of the oxo complexes differentiates sterically between the cap (alpha(2)) site and the belt (alpha(1)) site in the Wells-Dawson structure (alpha(2)()2 dimerizes in high yield; alpha(1)()2 does not). All four POMs exhibit high activity in cell culture against HIV-1 (EC(50) values of 0.17-0.83 microM), are minimally toxic (IC(50) values of 50 to >100 microM), and selectively inhibit purified HIV-1 protease (HIV-1P) (IC(50) values for alpha(1)()1, alpha(2)()1, alpha(1)()2, and alpha(2)()2 of 2.0, 1.2, 1.5, and 1.8 microM, respectively). Thus, theoretical, binding, and kinetics studies of the POM/HIV-1P interaction(s) were conducted. Parameters for [P(2)W(17)NbO(62)](7)(-) were determined for the Kollman all-atom (KAA) force field in Sybyl 6.2. Charges for the POM were obtained from natural population analysis (NPA) at the HF/LANL2DZ level of theory. AutoDock 2.2 was used to explore possible binding locations for the POM with HIV-1P. These computational studies strongly suggest that the POMs function not by binding to the active site of HIV-1P, the mode of inhibition of all other HIV-1P protease inhibitors, but by binding to a cationic pocket on the "hinge" region of the flaps covering the active site (2 POMs and cationic pockets per active homodimer of HIV-1P). The kinetics and binding studies, conducted after the molecular modeling, are both in remarkable agreement with the modeling results: 2 POMs bind per HIV-1P homodimer with high affinities (K(i) = 1.1 +/- 0.5 and 4.1 +/- 1.8 nM in 0.1 and 1.0 M NaCl, respectively) and inhibition is noncompetitive (k(cat) but not K(m) is affected by the POM concentration).
authors.affiliation: Contribution from the Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Judd
authors.forename: J H
authors.initials: JH
authors.lastname: Nettles
authors.forename: N
authors.initials: N
authors.lastname: Nevins
authors.forename: J P
authors.initials: JP
authors.lastname: Snyder
authors.forename: D C
authors.initials: DC
authors.lastname: Liotta
authors.forename: J
authors.initials: J
authors.lastname: Tang
authors.forename: J
authors.initials: J
authors.lastname: Ermolieff
authors.forename: R F
authors.initials: RF
authors.lastname: Schinazi
authors.forename: C L
authors.initials: CL
authors.lastname: Hill
mesh_terms: D019380:Anti-HIV Agents / Q000737:chemistry / Q000494:pharmacology*; D002460:Cell Line; D017320:HIV Protease Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D015497:HIV-1 / Q000201:enzymology*; D008826:Microbial Sensitivity Tests; D017973:Tungsten Compounds / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D019380:Anti-HIV Agents; D017320:HIV Protease Inhibitors; D017973:Tungsten Compounds