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Contrasting features in the assembly of Sesbania mosaic virus and Physalis mottle virus

Murthy, MRN (2008) Contrasting features in the assembly of Sesbania mosaic virus and Physalis mottle virus. In: Indian Journal Of Virology, 19 (1). p. 51.

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Abstract

Viruses have served as excellent model systems for studies on the assembly/disassembly of macromolecular complexes. We have studied the structures and molecular mechanisms of assembly of two icosahedral ss-RNA plant viruses, Sesbania mosaic virus (SeMV) and Physalis mottle virus (PhMV). The expression of CP gene of these viruses in E. coli was shown to result in the assembly of T=3 virus-like particles (VLPs). In SeMV, the recombinant T=3 particles encapsidate E. coli 23s rRNA and CP mRNA. Deletion of 31 or more amino acids from the N-terminus resulted in the formation of T=1 particles. X-ray diffraction data of three recombinant T=3 capsids and five recombinant T=1 capsids were collected and their structures were solved. A unique structure called b-annulus is found at the icosahedral three-folds of SeMV and many other T=3 viruses. It has been suggested that this structure is essential for T=3 capsid assembly. The structures of recombinant rCP and CP-P53A capsids indicate that despite the differences in the nucleic acid that is encapsidated and the manipulation of the crucial proline at the â-annulus, the core of the CP and the interactions at various interfaces are nearly identical to those of wild type particles. Surprisingly, deletion of residues involved in the formation of b-annulus did not affect capsid assembly. X-ray structural studies have revealed that the b-annulus is indeed absent in these capsids. The structures of T=1 mutants retain accurately several key intersubunit interactions of the native virus. Metal-ion mediated inter-subunit interactions increase the stability of SeMV but are not crucial for the assembly. An arginine rich motif found at the N-terminus of SeMV coat protein has been shown to be essential for RNA encapsidation. These studies have allowed proposition of a plausible model for the assembly of SeMV. The structural, mutational and immunological analysis of PhMV assembly has shown that the N-terminal arm is dynamic and could mediate an early step in the disassembly/assembly of the virus. Several mutants that disrupt interfacial interactions have been generated and their stability and assembly have been investigated. The results show that the coat protein folding and assembly are concerted events in the assembly of PhMV.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Indian Virological Society.
Department/Centre: Division of Biological Sciences > Biochemistry
Date Deposited: 30 Apr 2009 04:25
Last Modified: 30 Apr 2009 04:25
URI: http://eprints.iisc.ernet.in/id/eprint/17828

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