STRUCTURE OF A COVALENTLY TRAPPED CATALYTIC COMPLEX OF HIV-I REVERSE-TRANSCRIPTASE - IMPLICATIONS FOR DRUG-RESISTANCE

A combinatorial disulfide cross-linking strategy was used to prepare a stalled complex of human immunodeficiency virus-type 1 (HIV-1) revers e transcriptase with a DNA template:primer and a deoxynucleoside triph osphate (dNTP), and the crystal structure of the complex was determine d at a resolution of 3.2 angstroms. The presence of a dideoxynucleotid e at the 3'-primer terminus allows capture of a state in which the sub strates are poised for attack on the dNTP. Conformational changes that accompany formation of the catalytic complex produce distinct cluster s of the residues that are altered in viruses resistant to nucleoside analog drugs. The positioning of these residues in the neighborhood of the dNTP helps to resolve some Long-standing puzzles about the molecu lar basis of resistance. The resistance mutations are Likely to influe nce binding or reactivity of the inhibitors, relative to normal dNTPs, and the clustering of the mutations correlates with the chemical stru cture of the drug.