Dengue type 4 (DEN4) and other flaviviruses employ host and viral proteases for polyprotein processing. Most proteolytic cleavages in the DEN4 nonstructural protein (NS) region are mediated by the viral NS2B-NS3 protease. The N-terminal third of NS3, containing sequences homologous to serine protease active sites, is the protease domain. To determine required sequences in NS2B, deletions were introduced into DEN4 NS2B-30% NS3 cDNA and the expressed polyproteins assayed for self-cleavage. A 40 amino acid segment within NS2B was essential. Sequence analysis of NS2B predicts that this segment constitutes a hydrophilic domain surrounded by hydrophobic regions. Hydrophobicity profiles of other flavivirus NS2Bs show similar patterns. Cleavage of DEN4 NS1-NS2A requires an octapeptide sequence at the NS1 C terminus and downstream NS2A. Comparison of the analogous octapeptide sequences among flaviviruses indicates a consensus cleavage sequence of (P8)/Met/Leu-Val-Xaa-Ser-Xaa-Val-Ala(P1), where Xaa are non-conserved amino acids. The effects on cleavage of amino acid substitutions in this consensus sequence were analyzed. Most substitutions of the conserved residues interfered with cleavage, whereas substitutions of non-conserved residues had little or no effect. These findings indicate that the responsible enzyme recognizes well-defined sequences at the cleavage site.
CITATION STYLE
Lai, C. J., Pethel, M., Jan, L. R., Kawano, H., Cahour, A., & Falgout, B. (1994). Processing of dengue type 4 and other flavivirus nonstructural proteins. Archives of Virology. Supplementum, 9, 359–368. https://doi.org/10.1007/978-3-7091-9326-6_36
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