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Antimicrobial Agents and Chemotherapy, 07 1995, 1430-1435, Vol 39, No. 7
A Severini, XY Liu, JS Wilson and DL Tyrrell
We have used the endogenous reverse transcriptase reaction of viral core
particles from duck liver to elucidate the mechanism of inhibition of duck
hepatitis B virus (DHBV) replication by the nucleoside analog (-
)-beta-L-2',3'-dideoxy-3'-thiacytidine (3TC). As is the case in human
immunodeficiency virus replication, 3TC-5'-triphosphate (3TC-TP) acts as a
chain terminator for the DNA polymerase activities. The results of several
different experiments support this conclusion, which explains the potent
activity of 3TC against the hepadnaviruses. In isolated DHBV core
particles, 3TC-TP inhibited the reverse transcriptase in a manner that
resembled competitive inhibition with respect to dCTP. However, the
kinetics of inhibition was not linear on a double-reciprocal plot for the
highest concentrations of 3TC-TP and the lowest concentration of dCTP. This
anomaly would be expected if binding to the nucleotide site was followed by
DNA chain termination. Calculations that used only the linear part of the
curve yielded a Ki of 0.78 +/- 0.10 microM 3TC- TP. The inhibition of core
particles incubated in vitro with 3TC-TP was not reversed by removal of the
free inhibitor. 3TC-TP inactivated the reverse transcriptase activity in a
concentration-dependent manner. The Km of the chain termination reaction
was calculated at 0.71 +/- 0.05 microM. Similar competitive kinetics and
irreversible inhibition were also obtained on the endogenous DNA polymerase
from viral particles from serum, suggesting that 3TC-TP also acts as a
chain terminator of the DNA-directed DNA polymerase of DHBV
replication.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Mechanism of inhibition of duck hepatitis B virus polymerase by (-)- beta-L-2',3'-dideoxy-3'-thiacytidine
Glaxo Heritage Research Institute, Department of Medical Microbiology and Infectious Diseases, University of Alberta, Edmonton, Canada.
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