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PDBsum entry 1js9
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Contents |
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149 a.a.
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165 a.a.
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189 a.a.
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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The crystallographic structure of brome mosaic virus.
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Authors
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R.W.Lucas,
S.B.Larson,
A.Mcpherson.
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Ref.
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J Mol Biol, 2002,
317,
95.
[DOI no: ]
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PubMed id
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Abstract
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The structure of brome mosaic virus (BMV), the type member of the bromoviridae
family, has been determined from a single rhombohedral crystal by X-ray
diffraction, and refined to an R value of 0.237 for data in the range 3.4-40.0
A. The structure, which represents the native, compact form at pH 5.2 in the
presence of 0.1 M Mg(2+), was solved by molecular replacement using the model of
cowpea chlorotic mottle virus (CCMV), which BMV closely resembles. The BMV model
contains amino acid residues 41-189 for the pentameric capsid A subunits, and
residues 25-189 and 1-189 for the B and C subunits, respectively, which compose
the hexameric capsomeres. In the model there are two Mg ions and one molecule of
polyethylene glycol (PEG). The first 25 amino acid residues of the C subunit are
modeled as polyalanine. The coat protein has the canonical "jellyroll"
beta-barrel topology with extended amino-terminal polypeptides as seen in other
icosahedral plant viruses. Mass spectrometry shows that in native BMV virions, a
significant fraction of the amino-terminal peptides are apparently cleaved. No
recognizable nucleic acid residue is visible in the electron density maps except
at low resolution where it appears to exhibit a layered arrangement in the
virion interior. It is juxtaposed closely with the interior surface of the
capsid but does not interpenetrate. The protein subunits forming hexameric
capsomeres, and particularly dimers, appear to interact extensively, but the
subunits otherwise contact one another sparsely about the 5-fold and quasi
3-fold axes. Thus, the virion appears to be an assembly of loosely associated
hexameric capsomeres, which may be the basis for the swelling and dissociation
that occurs at neutral pH and elevated salt concentration. A Mg ion is observed
to lie exactly on the quasi-3-fold axis and is closely coordinated by
side-chains of three quasi-symmetry-related residues glutamates 84, with
possible participation of side-chains from threonines 145, and asparagines 148.
A presumptive Mg(2+) is also present on the 5-fold axis where there is a
concentration of negatively charged side-chains, but the precise coordination is
unclear. In both cases these cations appear to be essential for maintenance of
virion stability. Density that is contiguous with the viral interior is present
on the 3-fold axis at the center of the hexameric capsomere, where there is a
pore of about 6 A diameter. The density cannot be attributed to cations and it
was modeled as a PEG molecule.
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Figure 5.
Figure 5. The coordination of the Mg ion on the
quasi-3-fold axis. The glutamate, threonine, and aspartate
residues involved are labeled. These cations may serve a crucial
role in the formation and maintenance of the capsid structure,
and the carboxyl groups are likely those earlier identified as
Caspar carboxyls.[13]
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Figure 8.
Figure 8. Backbone representation superimposing the BMV ABC
trimer on the corresponding CCMV trimer, which is presented as a
transparent overlay.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2002,
317,
95-0)
copyright 2002.
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Secondary reference #1
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Title
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Crystallization of brome mosaic virus and t = 1 brome mosaic virus particles following a structural transition.
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Authors
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R.W.Lucas,
Y.G.Kuznetsov,
S.B.Larson,
A.Mcpherson.
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Ref.
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Virology, 2001,
286,
290-303.
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PubMed id
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