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PDBsum entry 1z1u
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Virus/viral protein
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PDB id
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1z1u
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References listed in PDB file
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Key reference
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Title
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Structural and functional similarities between the capsid proteins of bacteriophages t4 and hk97 point to a common ancestry.
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Authors
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A.Fokine,
P.G.Leiman,
M.M.Shneider,
B.Ahvazi,
K.M.Boeshans,
A.C.Steven,
L.W.Black,
V.V.Mesyanzhinov,
M.G.Rossmann.
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Ref.
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Proc Natl Acad Sci U S A, 2005,
102,
7163-7168.
[DOI no: ]
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PubMed id
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Abstract
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Gene product (gp) 24 of bacteriophage T4 forms the pentameric vertices of the
capsid. Using x-ray crystallography, we found the principal domain of gp24 to
have a polypeptide fold similar to that of the HK97 phage capsid protein plus an
additional insertion domain. Fitting gp24 monomers into a cryo-EM density map of
the mature T4 capsid suggests that the insertion domain interacts with a
neighboring subunit, effecting a stabilization analogous to the covalent
crosslinking in the HK97 capsid. Sequence alignment and genetic data show that
the folds of gp24 and the hexamer-forming capsid protein, gp23*, are similar.
Accordingly, models of gp24* pentamers, gp23* hexamers, and the whole capsid
were built, based on a cryo-EM image reconstruction of the capsid. Mutations in
gene 23 that affect capsid shape map to the capsomer's periphery, whereas
mutations that allow gp23 to substitute for gp24 at the vertices modify the
interactions between monomers within capsomers. Structural data show that capsid
proteins of most tailed phages, and some eukaryotic viruses, may have evolved
from a common ancestor.
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Figure 1.
Fig. 1. A cryo-EM reconstruction at 22.5-Å resolution
of the T4 head capsid is shown. The gene products 23, 24, hoc,
and soc are colored blue, magenta, yellow, and pink,
respectively. The reconstruction used 5-fold averaging about the
long axis of the head. The features of the tail (green) appear
blurred because the tail has six-fold symmetry. [Adapted from
Fokine et al. (2).
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Figure 3.
Fig. 3. Stereo diagram shows the superposition of the C
 backbones of T4 gp24
(red) and the HK97 capsid protein (blue).
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