1a6c
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STRUCTURE OF TOBACCO RINGSPOT VIRUS
OverviewOverview
BACKGROUND: Tobacco ringspot virus (TRSV) is a member of the nepovirus, genus of icosahedral RNA plant viruses that cause disease in fruit crops., Nepoviruses, comoviruses and picornaviruses are classified in the, picornavirus superfamily. Crystal structures of comoviruses and, picornaviruses and the molecular mass of the TRSV subunit (sufficient to, accommodate three beta-barrel domains) suggested that nepoviruses may, represent a link in the evolution of the picornavirus capsids from a T = 3, icosahedral virus. This evolutionary process is thought to involve, triplication of the capsid protein gene, to encode a three-domain, polyprotein, followed by development of cleavage sites in the interdomain, linking regions. Structural studies on TRSV were initiated to determine if, the TRSV subunit corresponds to the proposed uncleaved three-domain, polyprotein. RESULTS: The 3.5 A resolution structure of TRSV shows that, the capsid protein consists of three beta-barrel domains covalently linked, by extended polypeptides. The order of connectivity of the domains in TRSV, confirms the proposed connectivity for the precleaved comovirus and, picornavirus capsid polyprotein. Structural differences between equivalent, domains in TRSV and comoviruses are confined to the external surface, loops, interdomain connecting polypeptides and N termini. The three, different domains within TRSV and comoviruses are more closely related at, the structural level than the three individual domains within, picornaviruses. CONCLUSIONS: The structural results confirm the notion of, divergent evolution of the capsid polyproteins of nepoviruses, comoviruses, and picornaviruses from a common ancestor. A number of residues were found, to be conserved among various nepoviruses, some of which stabilize the, quaternary structure of the three domains in the TRSV capsid protein, subunit. Two conserved regions were identified on the external surface of, TRSV, however, mutational studies will be needed to understand their, functional significance. Nepoviruses transmitted by the same nematode, species do not share regions with similar amino acid composition on the, viral surface.
About this StructureAbout this Structure
1A6C is a Single protein structure of sequence from Tobacco ringspot virus. Full crystallographic information is available from OCA.
ReferenceReference
The structure of tobacco ringspot virus: a link in the evolution of icosahedral capsids in the picornavirus superfamily., Chandrasekar V, Johnson JE, Structure. 1998 Feb 15;6(2):157-71. PMID:9519407
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