SERINE-PROTEASE OF PESTIVIRUSES - DETERMINATION OF CLEAVAGE SITES

The single-stranded genomic RNA of pestiviruses is of positive polarit y and encompasses one large open reading frame of about 4,000 codons, The resulting polyprotein is processed co- and posttranslationally by virus-encoded and host cell proteases to give rise to the mature viral proteins, A serine protease residing in the nonstructural (NS) protei n NS3 (p80) has been shown to be essential for the release of the NS p roteins located downstream of NS3, In this report the NS3 serine prote ase-dependent cleavage sites for bovine viral diarrhea virus (BVDV) st rain CP7 are described, Proteins used for analysis were generated in E scherichia coli or in eukaryotic cells by the use of the T7 vaccinia v irus system, The N termini of NS4A, NS4B, NS5A, and NS5B were determin ed by protein sequencing, Analysis of the data obtained showed that le ucine at P1 is the only position conserved for all cleavage sites, At P1' alanine is found at the NS4A-NS4B site, whereas serine resides at this position at the NS3-NS4A, NS4B-NS5A, and NS5A-NS5B cleavage sites , For all cleavage sites the amino acids found at P1 and P1' are conse rved for different genotypes of pestiviruses, despite the high degree of sequence variation found between these viruses, It is therefore ass umed that the cleavage sites determined for BVDV CP7 are representativ e of those for all pestiviruses.