Characterization of the catalytic residues of the tobacco etch virus 49-kDa proteinase

Virology. 1989 Sep;172(1):302-10. doi: 10.1016/0042-6822(89)90132-3.


The 49-kDa proteinase of tobacco etch virus (TEV) cleaves the polyprotein derived from the TEV genomic RNA at five locations. Molecular genetic and biochemical analyses of the 49-kDa TEV proteinase were performed to test its homology to the cellular trypsin-like serine proteases. A cDNA fragment, containing the TEV 49-kDa proteinase gene and flanking sequences, was expressed in a cell-free transcription/translation system and resulted in the formation of a polyprotein precursor that underwent rapid self-processing. Site-directed mutagenesis was used to test the effect of altering individual 49-kDa amino acid residues on proteolysis. The data suggest that the catalytic triad of the TEV 49-kDa proteinase could be composed of the His234, Asp269, and Cys339. These findings are consistent with the hypothesis that the TEV 49-kDa proteinase is structurally similar to the trypsin-like family of serine proteinases with the substitution of Cys339 as the active site nucleophile. A structural model of the TEV 49-kDa proteinase proposes other virus-specific differences in the vicinity of the active site triad and substrate-binding pocket. The structure may explain the observed negligible effect of most cellular proteinase inhibitors on the activity of this viral proteinase.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aprotinin / pharmacology
  • Binding Sites
  • DNA Mutational Analysis
  • Genes, Viral
  • Leupeptins / pharmacology
  • Papain / antagonists & inhibitors
  • Peptide Hydrolases / genetics
  • Peptide Hydrolases / metabolism*
  • Plant Viruses / enzymology*
  • Substrate Specificity
  • Viral Proteins / genetics
  • Zinc / pharmacology


  • Leupeptins
  • Viral Proteins
  • Aprotinin
  • Peptide Hydrolases
  • Papain
  • Zinc
  • leupeptin