Lamivudine (3TC) resistance in HIV-1 reverse transcriptase involves steric hindrance with beta-branched amino acids.Sarafianos, S.G., Das, K., Clark Jr., A.D., Ding, J., Boyer, P.L., Hughes, S.H., Arnold, E.
(1999) Proc.Natl.Acad.Sci.USA 96: 10027-10033
- PubMed: 10468556
- Primary Citation of Related Structures:  1J5O
- PubMed Abstract:
- Structure and Functional Implications of the Polymerase Active Site Region in a Complex of HIV-1 RT with a Double-Stranded DNA and an Antibody Fab Fragment at 2.8 Angstroms Resolution
Ding, J.,Das, K.,Hsiou, Y.,Sarafianos, S.G.,Clark Jr., A.D.,Jacobo-Molina, A.,Tantillo, C.,Hughes, S.H.,Arnold, E.
(1998) J.Mol.Biol. 284: 1095
- Structure of Unliganded HIV-1 Reverse Transcriptase at 2.7 A resolution: Implications of conformational changes for polymerization and inhibition mechanisms
Hsiou, Y.,Ding, J.,Das, K.,Clark Jr., A.D.,Hughes, S.H.,Arnold, E.
(1996) Structure 4: 853
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 ...
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.
Center for Advanced Biotechnology and Medicine (CABM) and Rutgers University Chemistry Department, 679 Hoes Lane, Piscataway, NJ 08854-5638, USA.