Processing of dengue type 4 and other flavivirus nonstructural proteins.
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.
Lai
C J
CJ
Molecular Viral Biology Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland.
Pethel
M
M
Jan
L R
LR
Kawano
H
H
Cahour
A
A
Falgout
B
B
D000595:Amino Acid Sequence; D004252:DNA Mutational Analysis; D003716:Dengue Virus / Q000378:metabolism*; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D020365:RNA Helicases; D011994:Recombinant Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014616:Vaccinia virus / Q000235:genetics; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
D020365:RNA Helicases; D011994:Recombinant Proteins; D012697:Serine Endopeptidases; D017361:Viral Nonstructural Proteins; C080102:NS2B protein, flavivirus; C060028:NS3 protein, flavivirus; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases