摘要 : Pestivirus N~(pro) is the first protein translated in the viral polypeptide, and cleaves itself off co-translationally generating the N-terminus of the core protein. Once released, N~(pro) blocks the host's interferon response by ... 展开 Pestivirus N~(pro) is the first protein translated in the viral polypeptide, and cleaves itself off co-translationally generating the N-terminus of the core protein. Once released, N~(pro) blocks the host's interferon response by inducing degradation of interferon regulatory factor-3. N~(pro)'s intracellular autocatalytic activity and lack of trans-activity have hampered in vitro cleavage studies to establish its substrate specificity and the roles of individual residues. We constructed N~(pro)-GFP fusion proteins that carry the authentic cleavage site and determined the autoproteolytic activities of N~(pro) proteins containing substitutions at the predicted catalytic sites Glu22 and Cys69, at ArglOO that forms a salt bridge with Glu22, and at the cleavage site Cysl68. Contrary to previous reports, we show that N~(pro)'s catalytic activity does not involve Glu22, which may instead be involved in protein stability. Furthermore, NN~(pro) does not have specificity for Cysl68 at the cleavage site even though this residue is conserved throughout the pestivirus genus. 收起