The larger ORF encodes a 110-kD a polyprotein precursor that can be cleaved by the proteolytic activity of VP4 into the precursor ofVP2, VP3 and VP4.During virion maturation, pVP2 is further processed into them ature capsid protein VP2 and four small peptides.VP2 carries the major immunogenic Palbociclib Isethionate determinants and contributes significantly to apoptosis, cell tropism, virulence and pathogenicity of virulent IBDV.VP3, a major immunogenic and scaffolding protein of IBDV, was found to interact with VP1 and bind to the viral dsRNA forming ribonucleoprotein complexes, as well as thought to be a key organizer in virion morphogenesis.VP4,as the viral protease of Birna viruses, has been proposed to utilize a Ser/Lyscatalytic dyad mechanism to process the polyprotein. VP4 forms regular needle-like structures called type II tubules with in the cytoplasm and nucleus of IBDV-infected cells. Mean while, current research data shows that E.coli-expressed VP4 protein can self-assemble into functional tubule-like particles and its activity can be completely inhibited by 1mM of Ni2+ ions. Recently, more attention has been paid to the functions of viral protein phosphorylation during virus infection. Phosphorylation at the Ser224 site of ICP0 of herpes simplex virus type 1 is known to be required for efficient viral replication. Phosphorylated sites at Ser479 and Ser510 of the N protein in measles virus are important for the activation of viral mRNA transcription and/or Imidurea replication of the genome in vivo. In hepatitis Cvirus, the phosphorylated site at Ser222 of NS5A functions as a negative regulator of RNA replication. The phosphorylation ofSer60, Ser64, andThr62of thePprotein of vesicular stomatitis virus iscritical for viralgenome RNA encapsidation and template function. Dephosphorylation of VP40 at sites Tyr7,Tyr10, Tyr13 and Tyr19 of Marburg virus impairs its ability to recruit nucleocapsid structures into filopodia, causing release of virions with low infectivity. Phosphorylation of the capsid protein of West Nile virus mediated by protein kinase Chas been shown to enhance its binding to HDM2 protein and import in and subsequently induce p53-dependent apoptosis.