Epitopes described in "Lamivudine (3TC) resistance in HIV-1 reverse transcriptase involves steric hindrance with beta-branched amino acids."

Reference
Article Authors:S G Sarafianos; K Das; A D Clark Jr; J Ding; P L Boyer; S H Hughes; E Arnold
Article Title:Lamivudine (3TC) resistance in HIV-1 reverse transcriptase involves steric hindrance with beta-branched amino acids.
Reference Detail
Reference ID:1096
Abstract:An important component of triple-drug anti-AIDS therapy is 2', 3'-dideoxy-3'-thiacytidine (3TC, lamivudine). Single mutations at residue 184 of the reverse transcriptase (RT) in HIV cause high-level resistance to 3TC and contribute to the failure of anti-AIDS combination therapy. We have determined crystal structures of the 3TC-resistant mutant HIV-1 RT (M184I) in both the presence and absence of a DNA/DNA template-primer. In the absence of a DNA substrate, the wild-type and mutant structures are very similar. However, comparison of crystal structures of M184I mutant and wild-type HIV-1 RT with and without DNA reveals repositioning of the template-primer in the M184I/DNA binary complex and other smaller changes in residues in the dNTP-binding site. On the basis of these structural results, we developed a model that explains the ability of the 3TC-resistant mutant M184I to incorporate dNTPs but not the nucleotide analog 3TCTP. In this model, steric hindrance is expected for NRTIs with beta- or L- ring configurations, as with the enantiomer of 3TC that is used in therapy. Steric conflict between the oxathiolane ring of 3TCTP and the side chain of beta-branched amino acids (Val, Ile, Thr) at position 184 perturbs inhibitor binding, leading to a reduction in incorporation of the analog. The model can also explain the 3TC resistance of analogous hepatitis B polymerase mutants. Repositioning of the template-primer as observed in the binary complex (M184I/DNA) may also occur in the catalytic ternary complex (M184I/DNA/3TCTP) and contribute to 3TC resistance by interfering with the formation of a catalytically competent closed complex.
Date:1999
Reference Type:Literature
PubMed ID:10468556
Journal:Proc Natl Acad Sci U S A
Journal Volume:96
Article Pages:10027-32
Journal ISSN:1091-6490
Article Chemical List:Macromolecular Substances;RNA, Viral;Lamivudine;HIV Reverse Transcriptase
Article MeSH List:Allosteric Regulation; Amino Acid Sequence; Amino Acid Substitution; Conserved Sequence; Dimerization; Drug Resistance, Microbial; HIV Reverse Transcriptase(chemistry; genetics; metabolism); HIV-1(drug effects; enzymology; genetics); Humans; Lamivudine(chemistry; pharmacology); Macromolecular Substances; Models, Molecular; Molecular Sequence Data; Nucleic Acid Conformation; Point Mutation; Protein Conformation; RNA, Viral(chemistry; metabolism); Templates, Genetic
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