# Structure of recombinant capsids formed by the $\beta$-annulus deletion mutant — rCP $(\Delta 48-59)$ of Sesbania mosaic virus

Pappachan, Anju and Subashchandrabose, Chinnathambi and Satheshkumar, PS and Savithri, HS and Murthy, MRN (2008) Structure of recombinant capsids formed by the $\beta$-annulus deletion mutant — rCP $(\Delta 48-59)$ of Sesbania mosaic virus. In: Virology, 375 (1). pp. 190-196.

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## Abstract

A unique feature of several T=3 icosahedral viruses is the presence of a structure called the $\beta$-annulus formed by extensive hydrogen bonding between protein subunits related by icosahedral three-fold axis of symmetry. This unique structure has been suggested as a molecular switch that determines the T=3 capsid assembly. In order to examine the importance of the $\beta$-annulus, a deletion mutant of Sesbania mosaic virus coat protein in which residues 48-59 involved in the formation of the $\beta$-annulus were deleted retaining the rest of the residues in the amino terminal segment (rCP ($\Delta 48-59))$ was constructed. When expressed in Escherichia coli, the mutant protein assembled into virus like particles of sizes close to that of the wild type virus particles. The purified capsids were crystallized and their three dimensional structure was determined at $3.6\AA$ resolution by X-ray crystallography. The mutant capsid structure closely resembled that of the native virus particles. However, surprisingly, the structure revealed that the assembly of the particles has proceeded without the formation of the $\beta$-annulus. Therefore, the $\beta$-annulus is not essential for T=3 capsid assembly as speculated earlier and may be formed as a consequence of the particle assembly. This is the first structural demonstration that the virus particle morphology with and without the$\beta$-annulus could be closely similar.

Item Type: Journal Article Copyright for this article belongs to Elsevier. Sesbania mosaic virus;beta-annulus;coat protein;virus assembly;X-ray crystallography. Division of Biological Sciences > Molecular Biophysics UnitDivision of Biological Sciences > Biochemistry 24 Sep 2008 06:30 19 Sep 2010 04:49 http://eprints.iisc.ernet.in/id/eprint/15850