       Document 0612
 DOCN  M9630612
 TI    Mechanism of inhibition of duck hepatitis B virus polymerase by
       (-)-beta-L-2',3'-dideoxy-3'-thiacytidine.
 DT    9603
 AU    Severini A; Liu XY; Wilson JS; Tyrrell DL; Glaxo Heritage Research
       Institute, Department of Medical; Microbiology and Infectious Diseases,
       University of Alberta,; Edmonton, Canada.
 SO    Antimicrob Agents Chemother. 1995 Jul;39(7):1430-5. Unique Identifier :
       AIDSLINE MED/96104876
 AB    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)
 DE    Animal  Antiviral Agents/*PHARMACOLOGY  Base Sequence  Ducks  DNA
       Polymerases/*ANTAGONISTS & INHIB  Hepatitis B Virus, Duck/DRUG
       EFFECTS/*ENZYMOLOGY/PHYSIOLOGY  Kinetics  Molecular Sequence Data
       Nucleotides/METABOLISM  RNA-Directed DNA Polymerase  Support, Non-U.S.
       Gov't  Viral Core Proteins/*ANTAGONISTS & INHIB  Virus Replication/DRUG
       EFFECTS  Zalcitabine/*ANALOGS & DERIVATIVES/PHARMACOLOGY  JOURNAL
       ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).

