Expression of the Potyvirus Genome: The Role of Proteolytic Processing.

摘要

The genome of tobacco etch virus (TEV) is initially expressed as a single polyprotein which is cleaved by two viral-encoded proteinases. One of these proteinases, a 49kDa protein, is thought to be structurally related to the trypsin family of serine proteinases, but with a catalytic triad composed of histidine, aspartic acid and cysteine residues. The 49kDa proteinase recognizes and extended seven amino acid sequence (P6 thru P(prime)1) at each cleavage site identified on the TEV polyprotein. This cleavage site contains both conserved and nonconserved amino acids positions. Cell-free studies suggest the nonconserved amino acid positions at a cleavage site influence the rate of processing by the 49kDa proteinase. The possibility of differential processing may be a mechanism of gene regulation during a potyviral replication cycle. 53 refs., 4 figs., 1 tab.