title: Effects of drug resistance mutations L100I and V106A on the binding of pyrrolobenzoxazepinone nonnucleoside inhibitors to the human immunodeficiency virus type 1 reverse transcriptase catalytic complex.
abstract: We have previously described a novel class of nonnucleoside reverse transcriptase (RT) inhibitors, the pyrrolobenzoxazepinone (PBO) and the pyridopyrrolooxazepinone (PPO) derivatives, which were effective inhibitors of human immunodeficiency virus type 1 (HIV-1) RT, either wild type or carrying known drug resistance mutations (G. Campiani et al., J. Med. Chem. 42:4462-4470, 1999). The lead compound of the PPO class, (R)-(-)-PPO464, was shown to selectively target the ternary complex formed by the viral RT with its substrates nucleic acid and nucleotide (G. Maga et al., J. Biol. Chem. 276:44653-44662, 2001). In order to better understand the structural basis for this selectivity, we exploited some PBO analogs characterized by various substituents at C-3 and by different inhibition potencies and drug resistance profiles, and we studied their interaction with HIV-1 RT wild type or carrying the drug resistance mutations L100I and V106A. Our kinetic and thermodynamic analyses showed that the formation of the complex between the enzyme and the nucleotide increased the inhibition potency of the compound PBO354 and shifted the free energy (energy of activation, DeltaG(#)) for inhibitor binding toward more negative values. The V106A mutation conferred resistance to PBO 354 by increasing its dissociation rate from the enzyme, whereas the L100I mutation mainly decreased the association rate. This latter mutation also caused a severe reduction in the catalytic efficiency of the RT. These results provide a correlation between the efficiency of nucleotide utilization by RT and its resistance to PBO inhibition.
authors.affiliation: Istituto di Genetica Molecolare IGM-CNR, Consiglio Nazionale delle Ricerche, 27100 Pavia, Italy.
authors.forename: Giada A
authors.initials: GA
authors.lastname: Locatelli
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Campiani
authors.forename: Reynel
authors.initials: R
authors.lastname: Cancio
authors.forename: Elena
authors.initials: E
authors.lastname: Morelli
authors.forename: Anna
authors.initials: A
authors.lastname: Ramunno
authors.forename: Sandra
authors.initials: S
authors.lastname: Gemma
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hübscher
authors.forename: Silvio
authors.initials: S
authors.lastname: Spadari
authors.forename: Giovanni
authors.initials: G
authors.lastname: Maga
mesh_terms: D000465:Algorithms; D002384:Catalysis; D004279:DNA, Viral / Q000096:biosynthesis; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D024882:Drug Resistance, Viral; D054303:HIV Reverse Transcriptase / Q000235:genetics*; D015497:HIV-1 / Q000187:drug effects / Q000201:enzymology; D007700:Kinetics; D009154:Mutation / Q000502:physiology; D009696:Nucleic Acids / Q000378:metabolism; D012367:RNA, Viral / Q000096:biosynthesis; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology*; D013816:Thermodynamics
chemical_list: D004279:DNA, Viral; D009696:Nucleic Acids; D012367:RNA, Viral; D018894:Reverse Transcriptase Inhibitors; D054303:HIV Reverse Transcriptase; D004259:DNA-Directed DNA Polymerase