The 35-kDa protein from the N-terminus of the potyviral polyprotein functions as a third virus-encoded proteinase. Academic Article uri icon


  • The polyprotein encoded by plant potyviruses is proteolytically processed to at least eight mature products by viral-encoded proteinases. While the proteinases that catalyze processing at most of the cleavage sites have been identified, the enzyme responsible for cleavage between the 35-kDa protein and helper component-proteinase (HC-Pro), near the N-terminus of the viral polyprotein, has not been mapped or characterized previously. Polyproteins containing the 35-kDa protein and HC-Pro were synthesized in the wheat germ system using defined RNA transcripts and were demonstrated to undergo proteolysis to generate products that resemble fully processed proteins. The C-terminal half of the 35-kDa protein was found to be required for proteolysis, whereas most of the HC-Pro sequence was dispensable. Amino acid substitutions affecting three positions, each of which are conserved in the 35-kDa protein encoded by five potyviruses, were shown to inhibit protein processing. These data suggest that the 35-kDa protein functions as a proteinase to cleave at its C-terminus. A model that accounts for all proteolytic processing events in the potyviral polyprotein is presented.

published proceedings

  • Virology

altmetric score

  • 3

author list (cited authors)

  • Verchot, J., Koonin, E. V., & Carrington, J. C.

citation count

  • 170

complete list of authors

  • Verchot, J||Koonin, EV||Carrington, JC

publication date

  • December 1991