2gsy
The 2.6A structure of Infectious Bursal Virus Derived T=1 Particles
Structural highlights
FunctionPOLS_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 (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. 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 (By similarity). 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 (By similarity). Structural peptide 4 is a small peptide derived from pVP2 C-terminus. It is essential for the virus viability (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 PubMedInfectious bursal disease virus (IBDV), a member of the Birnaviridae family, is a double-stranded RNA virus that causes a highly contagious disease in young chickens leading to significant economic losses in the poultry industry. The VP2 protein, the only structural component of the IBDV icosahedral capsid, spontaneously assembles into T=1 subviral particles (SVP) when individually expressed as a chimeric gene. We have determined the crystal structure of the T=1 SVP to 2.60 A resolution. Our results show that the 20 trimeric VP2 clusters forming the T=1 shell are further stabilized by calcium ions located at the threefold icosahedral axes. The structure also reveals a new unexpected domain swapping that mediates interactions between adjacent trimers: a short helical segment located close to the end of the long C-terminal arm of VP2 is projected toward the threefold axis of a neighboring VP2 trimer, leading to a complex network of interactions that increases the stability of the T=1 particles. Analysis of crystal packing shows that the exposed capsid residues, His253 and Thr284, determinants of IBDV virulence and the adaptation of the virus to grow in cell culture, are involved in particle-particle interactions. The 2.6-Angstrom structure of infectious bursal disease virus-derived T=1 particles reveals new stabilizing elements of the virus capsid.,Garriga D, Querol-Audi J, Abaitua F, Saugar I, Pous J, Verdaguer N, Caston JR, Rodriguez JF J Virol. 2006 Jul;80(14):6895-905. PMID:16809295[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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