Structure and assembly of Sesbania mosaic virus

Savithri, HS and Murthy, MRN (2010) Structure and assembly of Sesbania mosaic virus. In: Current Science (Bangalore), 98 (3). pp. 346-351.

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Abstract

Sesbania mosaic virus (SeMV) is a ss-RNA (4149 nt) plant sobemovirus isolated from farmer's field around Tirupathi, Andhra Pradesh. The viral capsid (30 nm diameter) consists of 180 copies of protein subunits (MW 29 kDa) organized with icosahedral symmetry. In order to understand the mechanism of assembly of SeMV, a large number of deletion and substitution mutants of the coat protein (CP) were constructed. Recombinant SeMV CP (rCP) as well as the N-terminal rCP deletion mutant Delta N22 were found to assemble in E. coli into virus-like particles (VLPs). Delta N36 and Delta N65 mostly formed smaller particles consisting of 60 protein subunits. Although particlem assembly was not affected due to the substitution of aspartates (D14 and D149) that coordinate calcium ions by asparagines, the stability of the resulting capsids was drastically reduced. Deletion of residues forming a characteristic beta-annulus at the icosahedral 3-folds did not affect the assembly of VLPs. Mutation of a single tryptophan, which occurs near the icosahedral fivefold axis to glutamate or lysine, resulted in the disruption of the capsid leading to soluble dimers that resembled the quasi-dimer structure of the native virus. Replacement of positively charged residues in the amino terminal segment of CP resulted in the formation of empty shells. Based on these observations, a plausible mechanism of assembly is proposed.

Item Type:	Journal Article
Publication:	Current Science (Bangalore)
Publisher:	Indian Academy of Sciences
Additional Information:	Copyright of this article belongs to Indian Academy of Sciences.
Keywords:	Coat protein dimer; icosahedral particles; mechanism of assembly; Sesbania mosaic virus
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit Division of Biological Sciences > Biochemistry
Date Deposited:	12 Apr 2010 08:10
Last Modified:	19 Sep 2010 05:59
URI:	http://eprints.iisc.ac.in/id/eprint/27044

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