Identification of protease and ADP-ribose 1''-monophosphatase activities associated with transmissible gastroenteritis virus non-structural protein 3.
الكلمات الدالة
نبذة مختصرة
The replicase polyproteins, pp1a and pp1ab, of porcine Transmissible gastroenteritis virus (TGEV) have been predicted to be cleaved by viral proteases into 16 non-structural proteins (nsp). Here, enzymic activities residing in the amino-proximal region of nsp3, the largest TGEV replicase processing product, were characterized. It was shown, by in vitro translation experiments and protein sequencing, that the papain-like protease 1, PL1(pro), but not a mutant derivative containing a substitution of the presumed active-site nucleophile, Cys(1093), cleaves the nsp2|nsp3 site at (879)Gly|Gly(880). By using an antiserum raised against the pp1a/pp1ab residues 526-713, the upstream processing product, nsp2, was identified as an 85 kDa protein in TGEV-infected cells. Furthermore, PL1(pro) was confirmed to be flanked at its C terminus by a domain (called X) that mediates ADP-ribose 1''-phosphatase activity. Expression and characterization of a range of bacterially expressed forms of this enzyme suggest that the active X domain comprises pp1a/pp1ab residues Asp(1320)-Ser(1486).