title: Evidence that the N-terminal domain of nonstructural protein NS3 from yellow fever virus is a serine protease responsible for site-specific cleavages in the viral polyprotein.
abstract: Sequence homology and molecular modeling studies have suggested that the N-terminal one-third of the flavirvirus nonstructural protein NS3 functions as a trypsin-like serine protease. To examine the putative proteolytic activity of NS3, segments of the yellow fever virus genome were subcloned into plasmid transcription/translation vectors and cell-free translation products were characterized. The results suggest that a protease activity encoded within NS2B and the N-terminal one-third of yellow fever virus NS3 is capable of cis-acting site-specific proteolysis at the NS2B-NS3 cleavage site and dilution-insensitive cleavage of the NS2A-NS2B site. Site-directed mutagenesis of the His-53, Asp-77, and Ser-138 residues of NS3 that compose the proposed catalytic triad implicates this domain as a serine protease. Infectious virus was not recovered from mammalian cells transfected with RNAs transcribed from full-length yellow fever virus cDNA templates containing mutations at Ser-138 (which abolish or dramatically reduce protease activity in vitro), suggesting that the protease is required for viral replication.
authors: Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, MO 63110-1093.
authors: T J
authors: TJ
authors: Chambers
authors: R C
authors: RC
authors: Weir
authors: A
authors: A
authors: Grakoui
authors: D W
authors: DW
authors: McCourt
authors: J F
authors: JF
authors: Bazan
authors: R J
authors: RJ
authors: Fletterick
authors: C M
authors: CM
authors: Rice
mesh_terms: D002213:Capsid / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D005814:Genes, Viral; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics*; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism*; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins / Q000378:metabolism; D015678:Viral Structural Proteins / Q000235:genetics; D015005:Yellow fever virus / Q000201:enzymology* / Q000235:genetics
chemical_list: D011498:Protein Precursors; D014758:Viral Core Proteins; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins; D015678:Viral Structural Proteins; D012697:Serine Endopeptidases