American Chemical Society
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Human Immunodeficiency Virus Type 1 Reverse Transcriptase Dimer Destabilization by 1-{Spiro[4‘ ‘-amino-2‘ ‘,2‘ ‘-dioxo-1‘ ‘,2‘ ‘-oxathiole-5‘ ‘,3‘- [2‘,5‘-bis-O-(tert-butyldimethylsilyl)-β-d-ribofuranosyl]]}-3-ethylthymine

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journal contribution
posted on 2000-01-22, 00:00 authored by Nicolas Sluis-Cremer, Gary I. Dmitrienko, Jan Balzarini, Maria-José Camarasa, Michael A. Parniak
The nonnucleoside inhibitor binding pocket is a well-defined region in the p66 palm domain of the human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT). This binding pocket opens toward the interface of the p66/p51 heterodimer and we have investigated whether ligand binding at or near this site induces structural changes that have an impact on the dimeric structure of HIV-1 RT. 1-[2‘,5‘-bis-O-(tert-butyldimethylsilyl]-3‘-spiro-5‘ ‘-(4‘ ‘-amino-1‘ ‘,2‘ ‘-oxathiole-2‘ ‘,2‘ ‘-dioxide)-3-ethylthymine (TSAOe3T) was found to destabilize the subunit interactions of both the p66/p51 heterodimer and p66/p66 homodimer enzymes. The Gibbs free energy of dimer dissociation (ΔGDH2O) is decreased with increasing concentrations of TSAOe3T, resulting in a loss in dimer stability of 4.0 and 3.2 kcal/mol for the p66/p51 and p66/p66 HIV-1 RT enzymes, respectively. This loss of energy is not sufficient to induce the dissociation of the subunits in the absence of denaturant. This destabilizing effect seems to be unique for TSAOe3T, since neither the tight-binding inhibitor UC781 nor nevirapine showed any effects on the stability of HIV-1 RT dimers. TSAOe3T was unable to destabilize the subunit interactions of the E138K mutant enzyme, which exhibits significant resistance to TSAOe3T inhibition. Molecular modeling of TSAOm3T into the nonnucleoside inhibitor binding pocket of wild-type RT suggests that it makes significant interactions with the p51 subunit of the enzyme, a feature that has not been observed with other types of nonnucleoside inhibitors. The observed destabilization of the dimeric HIV-1 RT may result from structural/conformational perturbations at the reverse transcriptase subunit interface.