1st International Workshop on HIV Drug Resistance & Treatment Strategies 25-28 June 1997, St. Petersburg, Florida, USA

STRUCTURAL EVIDENCE FOR NUCLEIC ACID REPOSITIONING BY THE Met184ile MUTANT OF HIV-1 REVERSE TRANSCRIPTASE AND IMPLICATIONS FOR DRUG RESISTANCE

Antiviral Therapy 1997;2 (Suppl 5):8 (abstract no. 12)

Stefan G Sarafianos¹, Kalyan Das¹, Jianping Ding¹, Arthur D Clark Jr¹, Patrick Clark², Paul L Boyer², Stephan H Hughes² and Edward Arnold^1
1Center for Advanced Biotechnology and Medicine (CABM) and Department of Chemistry, Rutgers University, Piscataway, New Jersey; and ²ABL-Basic Research Program, NCI Frederick Cancer Research and Development Center, Building 539, Frederick, Maryland, USA.

A single mutation at the Met184 residue of HIV-1 reverse transcriptase (RT) is sufficient to induce high level resistance to lamivudine and (-)-FTC. The same residue has been implicated in conferring modest resistance to didanosine and zalcitabine, and in restoring zidovudine sensitivity to zidovudine-resistant mutants. The viral escape involves initially a Met184Ile RT mutant that is followed and eventually outgrown by Met184Val. Although Met184 is the single most studied HIV-1 RT residue, the structural attributes of its involvement in the mechanism of drug resistance still remain elusive.

We have solved the Met184Ile crystal structure of HIV-1 RT in complex with a double-stranded DNA (19:18) at 3.5 Å resolution. Comparison with the structure of wild-type RT/19:18, previously solved in our laboratory, reveals a number of structural changes. A surprisingly substantial change in the position of the last few nucleotides of the primer strand was observed, which was most pronounced at the 3´ terminal nucleotide at the active site. Smaller changes were also observed for several template nucleotides. The side chain of Met184Ile interacts with the primer terminal nucleotide, thus affecting the position of the 3´-OH. Possibly related to this contact and to the primer rearrangement is a slight repositioning of the primer grip. Additional changes are observed in residues reported to be involved in dNTP binding, consistent with the reported influence of Met184 in the binding of dNTP and its analogues.

Analysis of our structural results is providing important information about how Met184Ile of HIV-1 RT can discriminate dNTP from some dNTP analogue inhibitors. Based on these results we are proposing a model for the structural basis of resistance to oxathiolane inhibitors.

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1997-06-25
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