THE QUINOLINE U-78036 IS A POTENT INHIBITOR OF HIV-1 REVERSE-TRANSCRIPTASE

The quinoline U-78036 represents a new class of non-nucleoside human i mmunodeficiency virus (HIV)-1 reverse transcriptase inhibitors. The ag ent possesses excellent antiviral activity at nontoxic doses in HIV-1- infected lymphocytes grown in tissue culture. Enzymatic kinetic studie s of the HIV-1 reverse transcriptase (RT)-catalyzed RNA-directed DNA p olymerase function were carried out in order to determine whether the inhibitor interacts with the template-primer or deoxyribonucleotide tr iphosphate (dNTP) binding sites of the polymerase. The data were analy zed using steady-state or Briggs-Haldane kinetics assuming that the te mplate-primer binds to the enzyme first followed by the dNTP and that the polymerase functions processively. The calculated rate constants a re in agreement with this model. The results show that the inhibitor a cts as a mixed to noncompetitive inhibitor with respect to both the te mplate-primer and the dNTP binding sites of the enzyme. Hence, U-78036 inhibits the RNA-directed DNA polymerase activity of RT by interactin g with a site distinct from the template-primer and dNTP binding sites . Moreover, the potency of U-78036 is dependent on the base compositio n of the template-primer. The equilibrium constants for various enzyme -substrate-inhibitor complexes were at least seven times lower for the poly(rC) . (dG)10-catalyzed system than the one catalyzed by poly(rA) .(dT)10. In addition, the inhibitor does not impair the DNA-dependent DNA polymerase activity and the RNase H function of HIV-1 RT nor does it inhibit the RNA-directed DNA polymerase activity of the HIV-2, avia n myoblastoma virus, and murine leukemia virus RT enzymes.