Structural highlights
Function
[POLS_IPNVS] Capsid protein VP2 self assembles to form an icosahedral capsid with a T=13 symmetry, about 70 nm in diameter, and consisting of 260 VP2 trimers. The capsid encapsulates the genomic dsRNA. VP2 is also involved in attachment and entry into the host cell (By similarity). The precursor of VP2 plays an important role in capsid assembly. First, pre-VP2 and VP2 oligomers assemble to form a procapsid. Then, the pre-VP2 intermediates may be processed into VP2 proteins by proteolytic cleavage mediated by VP4 to obtain the mature virion. The final capsid is composed of pentamers and hexamers but VP2 has a natural tendency to assemble into all-pentameric structures. Therefore pre-VP2 may be required to allow formation of the hexameric structures (By similarity). Protease VP4 is a serine protease that cleaves the polyprotein into its final products. Pre-VP2 is first partially cleaved, and may be completely processed by VP4 upon capsid maturation (By similarity). Capsid protein VP3 plays a key role in virion assembly by providing a scaffold for the capsid made of VP2. May self-assemble to form a T=4-like icosahedral inner-capsid composed of at least 180 trimers. Plays a role in genomic RNA packaging by recruiting VP1 into the capsid and interacting with the dsRNA genome segments to form a ribonucleoprotein complex. Additionally, the interaction of the VP3 C-terminal tail with VP1 removes the inherent structural blockade of the polymerase active site. Thus, VP3 can also function as a transcriptional activator (By similarity). Structural peptide 1 is a small peptide derived from pre-VP2 C-terminus. It destabilizes and perforates cell membranes, suggesting a role during entry (By similarity). Structural peptide 2 is a small peptide derived from pVP2 C-terminus. It is not essential for the virus viability, but viral growth is affected when missing (By similarity). Structural peptide 3 is a small peptide derived from pVP2 C-terminus. It is not essential for the virus viability, but viral growth is affected when missing (By similarity).
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
Infectious pancreatic necrosis virus (IPNV), an aquatic birnavirus that infects salmonid fish, encodes a large polyprotein (NH(2)-pVP2-VP4-VP3-COOH) that is processed through the proteolytic activity of its own protease, VP4, to release the proteins pVP2 and VP3. pVP2 is further processed to give rise to the capsid protein VP2 and three peptides that are incorporated into the virion. Reported here are two crystal structures of the IPNV VP4 protease solved from two different crystal symmetries. The electron density at the active site in the triclinic crystal form, refined to 2.2-A resolution, reveals the acyl-enzyme complex formed with an internal VP4 cleavage site. The complex was generated using a truncated enzyme in which the general base lysine was substituted. Inside the complex, the nucleophilic Ser(633)Ogamma forms an ester bond with the main-chain carbonyl of the C-terminal residue, Ala(716), of a neighboring VP4. The structure of this substrate-VP4 complex allows us to identify the S1, S3, S5, and S6 substrate binding pockets as well as other substrate-VP4 interactions and therefore provides structural insights into the substrate specificity of this enzyme. The structure from the hexagonal crystal form, refined to 2.3-A resolution, reveals the free-binding site of the protease. Three-dimensional alignment with the VP4 of blotched snakehead virus, another birnavirus, shows that the overall structure of VP4 is conserved despite a low level of sequence identity ( approximately 19%). The structure determinations of IPNV VP4, the first of an acyl-enzyme complex for a Ser/Lys dyad protease, provide insights into the catalytic mechanism and substrate recognition of this type of protease.
Crystal structure of the VP4 protease from infectious pancreatic necrosis virus reveals the acyl-enzyme complex for an intermolecular self-cleavage reaction.,Lee J, Feldman AR, Delmas B, Paetzel M J Biol Chem. 2007 Aug 24;282(34):24928-37. Epub 2007 Jun 6. PMID:17553791[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Lee J, Feldman AR, Delmas B, Paetzel M. Crystal structure of the VP4 protease from infectious pancreatic necrosis virus reveals the acyl-enzyme complex for an intermolecular self-cleavage reaction. J Biol Chem. 2007 Aug 24;282(34):24928-37. Epub 2007 Jun 6. PMID:17553791 doi:http://dx.doi.org/10.1074/jbc.M701551200
