Halogenated benzimidazoles and benzotriazoles as inhibitors of the NTPase/helicase activities of hepatitis C and related viruses

Eur J Biochem. 2003 Apr;270(8):1645-53. doi: 10.1046/j.1432-1033.2003.03540.x.

Abstract

A search has been initiated for lead inhibitors of the nonstructural protein 3 (NS3)-associated NTPase/helicase activities of hepatitis C virus, the related West Nile virus, Japanese encephalitis virus and the human mitochondrial Suv3 enzyme. Random screening of a broad range of unrelated low-molecular mass compounds, employing both RNA and DNA substrates, revealed that 4,5,6,7-tetrabromobenzotriazole (TBBT) hitherto known as a potent highly selective inhibitor of protein kinase 2, is a good inhibitor of the helicase, but not NTPase, activity of hepatitis C virus NTPase/helicase. The IC50 is approximately 20 micro m with a DNA substrate, but only 60 micro m with an RNA substrate. Several related analogues of TBBT were enzyme- and/or substrate-specific inhibitors. For example, 5,6-dichloro-1-(beta-d-ribofuranosyl)benzotriazole (DRBT) was a good, and selective, inhibitor of the West Nile virus enzyme with an RNA substrate (IC50 approximately 0.3 micro m), but much weaker with a DNA substrate (IC50 approximately 3 micro m). Preincubation of the enzymes, but not substrates, with DRBT enhanced inhibitory potency, e.g. the IC50 vs the hepatitis C virus helicase activity was reduced from 1.5 to 0.1 micro m. No effect of preincubation was noted with TBBT, suggesting a different mode of interaction with the enzyme. The tetrachloro congener of TBBT, 4,5,6,7,-tetrachlorobenzotriazole (TCBT; a much weaker inhibitor of casein kinase 2) is also a much weaker inhibitor than TBBT of all four helicases. Kinetic studies, supplemented by comparison of ATP-binding sites, indicated that, unlike the case with casein kinase 2, the mode of action of the inhibitors vs the helicases is not by interaction with the catalytic ATP-binding site, but rather by occupation of an allosteric nucleoside/nucleotide binding site. The halogeno benzimidazoles and benzotriazoles included in this study are excellent lead compounds for the development of more potent inhibitors of hepatitis C virus and other viral NTPase/helicases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Anhydride Hydrolases / antagonists & inhibitors*
  • Adenosine Triphosphatases / antagonists & inhibitors
  • Adenosine Triphosphatases / chemistry
  • Antiviral Agents / pharmacology
  • Benzimidazoles / pharmacology*
  • Binding Sites
  • DNA Helicases / antagonists & inhibitors*
  • Hepacivirus / drug effects
  • Hepacivirus / enzymology*
  • Kinetics
  • Models, Molecular
  • Nucleoside-Triphosphatase
  • Protein Conformation
  • Substrate Specificity
  • Triazoles / pharmacology*
  • Viral Nonstructural Proteins / antagonists & inhibitors
  • Viral Nonstructural Proteins / chemistry

Substances

  • Antiviral Agents
  • Benzimidazoles
  • NS3 protein, hepatitis C virus
  • Triazoles
  • Viral Nonstructural Proteins
  • benzotriazole
  • Acid Anhydride Hydrolases
  • Adenosine Triphosphatases
  • Nucleoside-Triphosphatase
  • DNA Helicases