Capsid structure of sesbania mosaic virus coat protein deletion mutant rcp(delta 48 to 59)
Structure:
Coat protein. Chain: a, b, c. Fragment: residues 1-47,60-268. Engineered: yes. Other_details: the residues 48 to 59 of the coat protein which are involved in the formation of a motif called the beta-annulus is deleted in the mutant rcp(delta 48-59)
A.Pappachan
et al.
(2008).
Structure of recombinant capsids formed by the beta-annulus deletion mutant -- rCP (Delta48-59) of Sesbania mosaic virus.
Virology,
375,
190-196.
PubMed id: 18295296
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 (Delta48-59)) 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 A 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.
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