Protein-Nucleic Acid Interactions and Dna Conformation in a Complex of Human Immunodeficiency Virus Type 1 Reverse Transcriptase With a Double-Stranded Dna Template-Primer

The conformation of the DNA and the interactions of the nucleic acid with the protein in a complex of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) and a 19-mer/18-mer double-stranded DNA template-primer (dsDNA) are described. The structure of this HIV-1 RT complex with dsDNA selves as a useful paradigm for studying aspects of nucleotide polymerases such as catalysis, fidelity, drug inhibition, and drug resistance. The bound dsDNA has a bend of approximately 41 degrees at the junction of an A-form region (first-five base pairs near the polymerase active site) and a B-form region (the last nine base pairs toward the RNase H active sire). The 41 degrees bend occurs smoothly over the four base pairs between the A-form portion and the B-form portion in the vicinity of helices alpha H and alpha I of the p66 thumb subdomain. The inter actions between the dsDNA and protein primarily involve the sugar-phosphate backbone of the nucleic acid and structural elements of the palm, thumb, and RNase H of p66, and are not sequence specific. Amino acid residues from the polymerase active site region, including amino acid residues of the conserved Sr-Met-Asp-Asp (YMDD) motif and the ''primer grip,'' interact with 3'-terminal nucleotides of the primer str-and and are involved in positioning the primer terminal nucleotide and its 3'-OH group at the polymerase active site. Amino acid residues of the ''template grip'' have close contacts with the template strand and aid in positioning the template strand near the polymerase active site. Helix alpha H of the p66 thumb is partly inserted into the minor groove of the dsDNA and helix alpha I is directly adjacent to the backbone of the template strand. Amino acid residues of beta 1', alpha A', alpha B', and the loop containing His539 of the RNase H domain interact with the primer strand of the dsDNA. (C) 1997 John Wiley & Sons, Inc. [References: 72]

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