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Description

Capsid scaffolding protein (UniProt: P89449, also known as Capsid protein P40, Nucleocapsid protein P40, Protease precursor, pPR, Virion structural protein UL26) is encoded by the UL26 gene (Gene ID: 1487310) in Herpes Simplex virus 2 (HSV-2). HSV-2 is a large complex DNA-containing virus that is shown to induce the synthesis of at least 50 new polypeptides in infected cells. It replicates in the nuclei of mammalian cells. Its nuclear localization signal is localized in amino acids 428-431. Following its synthesis, Capsid protein 40 is processed into Assemblin (aa 1-237), and Assembly protein (aa 248-637) by proteolytic cleavage. Assemblin is a protease that plays an essential role in virion assembly within the nucleus. It exists in a monomer-dimer equilibrium with the dimer being the active species. It catalyzes the cleavage of the assembly protein after formation of the spherical procapsid. By that cleavage, the capsid matures and gains its icosahedral shape. The assembly protein is involved in capsid assembly. It acts as a scaffold protein by binding major capsid protein and multimerizes in the nucleus such as major capsid protein forms the icosahedral T=16 capsid. It is cleaved by Assemblin after capsid completion and the cleavages products are evicted from the capsid before or during DNA packaging. HSV is reported to evade the immune system through interference with MHC class I antigen presentation on the cell surface, by blocking the transporter associated with antigen processing (TAP) induced by the secretion of infected cell protein 47 (ICP-47) by HSV. ICP-47 prevents initiation of a CTL-response against HSV, allowing the virus to survive for a protracted period in the host. (Ref.: Goldsmith, K., et a. (1998). J. Exp. Med. 187(3), 341-348, Heilman, CJ., et al. (1981). J. Virol. 40(2), 508-515).