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M9630251.TXT
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1996-02-27
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Document 0251
DOCN M9630251
TI Inactivation of human immunodeficiency virus type 1 reverse
transcriptase by oltipraz: evidence for the formation of a stable
adduct.
DT 9603
AU Chavan SJ; Bornmann WG; Flexner C; Prochaska HJ; Molecular Pharmacology
and Therapeutics Program, Memorial; Sloan-Kettering Cancer Center, New
York, New York 10021, USA.
SO Arch Biochem Biophys. 1995 Dec 1;324(1):143-52. Unique Identifier :
AIDSLINE MED/96095703
AB Oltipraz (5-pyrazinyl-4-methyl-1,2-dithiole-3-thione), which is
undergoing clinical evaluation as an anticarcinogen, also inhibits HIV-1
replication (IC50 approximately equal to 10 microM). The inactivation of
RT appears to be a relevant antiviral mechanism since oltipraz blocks
viral replication in acutely infected T-cell lines, but is ineffective
in chronically infected ACH-2 cells (H. J. Prochaska, W. G. Bornmann, P.
Baron, and B. Polsky (1995) Mol. Pharmacol. 48, 15-20). Since a
nucleophilic amino acid is a likely target for oltipraz, we assessed
whether the conserved cysteine residues of HIV-1 RT (38Cys or 280Cys)
were the target(s) for oltipraz, and we synthesized [Me 14C]oltipraz to
determine if oltipraz forms a stable adduct with RT. Thus, HIV-2 RT as
well as wild-type, 38Cys-->Ser, 280Cys-->Ser, and the Cys-->Ser double
mutant of HIV-1 RT were purified from the lysates of transformed
Escherichia coli strain DH5 alpha (A. Hizi, M. Shaharabany, R. Tal, and
S. H. Hughes (1992) J. Biol. Chem. 267, 1293-1297) via a purification
procedure that included (NH4)2SO4 fractionation followed by gel
filtration, dye-ligand, and ion-exchange chromatographies. Procion
yellow H4R was chosen as the dye-ligand chromatography since it was the
most potent and selective inhibitor of RT among seventy reactive dyes
that were screened. Mono Q anion-exchange chromatography with
diethanolamine (pH 9) resulted in the generation of heterodimeric RT
from a predominantly homodimeric enzyme preparation. Because the
instability of dilute RT preparations at room temperature rendered the
kinetic evaluation of inactivation difficult, we sought to identify
conditions that prevent denaturation of these enzymes. High
concentrations (25 mM) of MgCl2 had a stabilizing effect. Oltipraz
behaved kinetically as an irreversible inhibitor of all RTs purified,
and the kinetic constants for the inactivation of these enzymes were not
significantly different from wild-type HIV-1 RT (Ki = 17.0 +/- 4.1
microM; k3 = 0.214 +/- 0.051 h-1). In stark contrast, oltipraz neither
inhibited nor inactivated the Klenow fragment of DNA polymerase I, whose
subdomain structure is similar to the p66 subunit of RT. Wild-type RT
was incubated with 60 microM [Me 14C]oltipraz for 4 h and was then
subjected to gel filtration chromatography. The [14C] label comigrated
with RT with a stoichiometry of binding of 0.88 +/- 0.05 oltipraz per
inactivated RT subunit (N = 3 experiments), and the [14C] label remained
bound after treatment with 4 M urea.(ABSTRACT TRUNCATED AT 400 WORDS)
DE Antiviral Agents/METABOLISM/*PHARMACOLOGY Binding Sites
Chromatography, Affinity Comparative Study DNA Polymerase I/DRUG
EFFECTS Enzyme Stability/DRUG EFFECTS Escherichia coli/GENETICS
HIV-1/*ENZYMOLOGY/GENETICS Kinetics Magnesium/PHARMACOLOGY Mutation
Pyrazines/METABOLISM/*PHARMACOLOGY Recombinant
Proteins/BIOSYNTHESIS/DRUG EFFECTS/ISOLATION & PURIF Reverse
Transcriptase Inhibitors/METABOLISM/*PHARMACOLOGY RNA-Directed DNA
Polymerase/*DRUG EFFECTS/GENETICS/ISOLATION & PURIF/METABOLISM
Support, U.S. Gov't, P.H.S. JOURNAL ARTICLE
SOURCE: National Library of Medicine. NOTICE: This material may be
protected by Copyright Law (Title 17, U.S.Code).