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Crystal structure of infectious bursal disease virus VP2 subviral particle
Structural highlights
FunctionQ9WR38_IBDV 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 interacting with host ITGA4/ITGB1.[ARBA:ARBA00024715] 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.[ARBA:ARBA00025351][RuleBase:RU363030] 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.[PROSITE-ProRule:PRU00881][RuleBase:RU363030] Structural peptide 1 is a small peptide derived from pre-VP2 C-terminus. It destabilizes and perforates cell membranes, suggesting a role during entry.[ARBA:ARBA00025236][RuleBase:RU363030] Structural peptide 2 is a small peptide derived from pre-VP2 C-terminus. It is not essential for the virus viability, but viral growth is affected when missing.[RuleBase:RU363030] Structural peptide 3 is a small peptide derived from pre-VP2 C-terminus. It is not essential for the virus viability, but viral growth is affected when missing.[RuleBase:RU363030] 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.[ARBA:ARBA00024831][RuleBase:RU363030] 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 PubMedThe structural protein VP2 of infectious bursal disease virus (IBDV) spontaneously forms a dodecahedral T=1 subviral particle (SVP), and is a primary immunogen of the virus. In this study, the structure of IBDV SVP was determined in a cubic crystal and refined to 2.6A resolution. It contains 20 independent VP2 subunits in a crystallographic asymmetric unit. Each subunit is folded mainly into a shell domain and a protrusion domain, both with the Swiss-roll topology, plus a small helical base domain. Three VP2 subunits constitute a tight trimer, which is the building block of IBDV (sub)viral particles. The structure revealed a calcium ion bound to three pairs of symmetry-related Asp31 and Asp174 to stabilize the VP2 trimer. Our results of treatment of SVP with EGTA, a Ca(2+)-chelating reagent, indicated that the metal-ion may be important not only in maintaining highly stable quaternary structure but also in regulating the swelling and dissociation of the icosahedral particles. A Ca(2+)-dependent assembly pathway was thus proposed, which involves further interactions between the trimers. The 20 independent subunits showed conformational variations, with the surface loops of the protrusion domain being the most diverse. These loops are targets of the neutralizing antibodies. Several common interactions between the surface loops were clearly observed, suggesting a possible major conformation of the immunogenic epitopes. Crystal structure of infectious bursal disease virus VP2 subviral particle at 2.6A resolution: implications in virion assembly and immunogenicity.,Lee CC, Ko TP, Chou CC, Yoshimura M, Doong SR, Wang MY, Wang AH J Struct Biol. 2006 Jul;155(1):74-86. Epub 2006 Mar 31. PMID:16677827[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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