Analyses of the terminal sequences of West Nile virus structural proteins and of the in vitro translation of these proteins allow the proposal of a complete scheme of the proteolytic cleavages involved in their synthesis.
The proteolytic processes involved in the synthesis of the structural proteins of the West Nile (WN) flavivirus were analyzed: The carboxy-terminal sequences of the structural proteins were determined and the proteins translated in vitro in the presence of membranes from a mRNA coding for the structural polyprotein were analyzed. The results obtained indicate that the following proteolytic activities are involved in the synthesis and assembly of WN virus structural proteins: The growing peptide chain which contains the sequences of the structural proteins in the order C-pre-M-E is cleaved at three places by cellular signalase(s). This cleavage generates the primary amino acid sequence of the mature structural proteins pre-M and E (and the amino-terminus of the ensuing nonstructural protein NS 1). The amino-terminal part of the polyprotein containing the amino acid residues 1 to 123 is released as a molecule which migrates slightly slower than the mature viral core protein and which presumably is associated to the RER membranes via its carboxy-terminal sequence. This protein is called the anchored C virus particles the anchored C protein is converted into mature C protein by removal of the carboxy-terminal hydrophobic segment containing the amino acid residues 106 to 123. Presumably a virus-coded protease which can cleave the polyprotein after two basic amino acid residues is responsible for this cleavage. The cell-associated WN virus particles are constructed from the proteins C, pre-M, and E which contain the amino residues 1-105, 124-290, and 291-787 of the polyprotein, respectively. Cleavage of the pre-M protein between amino acid residues 215 and 216, presumably by a cellular enzyme located in the Golgi vesicles, and loss of the amino-terminal fragment of this protein are associated with the release of virus from the cells.
Nowak
T
T
Institut für Virologie, Justus-Liebig-Universität Giessen, Federal Republic of Germany.
Färber
P M
PM
Wengler
G
G
Wengler
G
G
D000595:Amino Acid Sequence; D002474:Cell-Free System; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006868:Hydrolysis; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010449:Peptide Mapping; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D014764:Viral Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D015678:Viral Structural Proteins; D014902:West Nile virus / Q000032:analysis / Q000378:metabolism*
D014764:Viral Proteins; D015678:Viral Structural Proteins