title: Avibirnavirus VP4 Protein Is a Phosphoprotein and Partially Contributes to the Cleavage of Intermediate Precursor VP4-VP3 Polyprotein.
abstract: Birnavirus-encoded viral protein 4 (VP4) utilizes a Ser/Lys catalytic dyad mechanism to process polyprotein. Here three phosphorylated amino acid residues Ser538, Tyr611 and Thr674 within the VP4 protein of the infectious bursal disease virus (IBDV), a member of the genus Avibirnavirus of the family Birnaviridae, were identified by mass spectrometry. Anti-VP4 monoclonal antibodies finely mapping to phosphorylated (p)Ser538 and the epitope motif 530PVVDGIL536 were generated and verified. Proteomic analysis showed that in IBDV-infected cells the VP4 was distributed mainly in the cytoskeletal fraction and existed with different isoelectric points and several phosphorylation modifications. Phosphorylation of VP4 did not influence the aggregation of VP4 molecules. The proteolytic activity analysis verified that the pTyr611 and pThr674 sites within VP4 are involved in the cleavage of viral intermediate precursor VP4-VP3. This study demonstrates that IBDV-encoded VP4 protein is a unique phosphoprotein and that phosphorylation of Tyr611 and Thr674 of VP4 affects its serine-protease activity.
authors.affiliation: Key Laboratory of Animal Virology of Ministry of Agriculture, Zhejiang University, Hangzhou, PR China; Shaoxing Center for Disease Control and Prevention, Shaoxing, PR China.
authors.forename: Sanying
authors.initials: S
authors.lastname: Wang
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors.forename: Boli
authors.initials: B
authors.lastname: Hu
authors.affiliation: Key Laboratory of Animal Virology of Ministry of Agriculture, Zhejiang University, Hangzhou, PR China.
authors.forename: Weiying
authors.initials: W
authors.lastname: Si
authors.affiliation: Key Laboratory of Animal Virology of Ministry of Agriculture, Zhejiang University, Hangzhou, PR China.
authors.forename: Lu
authors.initials: L
authors.lastname: Jia
authors.affiliation: Key Laboratory of Animal Virology of Ministry of Agriculture, Zhejiang University, Hangzhou, PR China; State Key Laboratory and Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, Zhejiang University, Hangzhou, PR China.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Animal Virology of Ministry of Agriculture, Zhejiang University, Hangzhou, PR China; College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China; State Key Laboratory and Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, Zhejiang University, Hangzhou, PR China.
authors.forename: Jiyong
authors.initials: J
authors.lastname: Zhou
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D002460:Cell Line; D002645:Chickens; D003599:Cytoskeleton / Q000821:virology; D018604:Epitope Mapping; D005347:Fibroblasts / Q000821:virology*; D015967:Gene Expression Regulation, Viral; D057809:HEK293 Cells; D006801:Humans; D007243:Infectious bursal disease virus / Q000235:genetics / Q000378:metabolism; D007526:Isoelectric Point; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D059748:Proteolysis; D015678:Viral Structural Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D010750:Phosphoproteins; D011498:Protein Precursors; C478245:VP4 protein, infectious bursal disease virus; D015678:Viral Structural Proteins