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PDBsum entry 2kca
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Viral protein
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PDB id
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2kca
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References listed in PDB file
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Key reference
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Title
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Structure of bacteriophage spp1 head-To-Tail connection reveals mechanism for viral DNA gating.
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Authors
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S.Lhuillier,
M.Gallopin,
B.Gilquin,
S.Brasilès,
N.Lancelot,
G.Letellier,
M.Gilles,
G.Dethan,
E.V.Orlova,
J.Couprie,
P.Tavares,
S.Zinn-Justin.
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Ref.
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Proc Natl Acad Sci U S A, 2009,
106,
8507-8512.
[DOI no: ]
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PubMed id
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Abstract
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In many bacterial viruses and in certain animal viruses, the double-stranded DNA
genome enters and exits the capsid through a portal gatekeeper. We report a
pseudoatomic structure of a complete portal system. The bacteriophage SPP1
gatekeeper is composed of dodecamers of the portal protein gp6, the adaptor
gp15, and the stopper gp16. The solution structures of gp15 and gp16 were
determined by NMR. They were then docked together with the X-ray structure of
gp6 into the electron density of the approximately 1-MDa SPP1 portal complex
purified from DNA-filled capsids. The resulting structure reveals that
gatekeeper assembly is accompanied by a large rearrangement of the gp15
structure and by folding of a flexible loop of gp16 to form an intersubunit
parallel beta-sheet that closes the portal channel. This stopper system prevents
release of packaged DNA. Disulfide cross-linking between beta-strands of the
stopper blocks the key conformational changes that control genome ejection from
the virus at the beginning of host infection.
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Figure 4.
Pseudoatomic structure of the SPP1 connector. Gp6 (blue),
gp15 (magenta), and gp16 (green) structures resulting from
separate docking in the EM connector maps were placed together
in the whole-connector reconstruction and refined by using UROX
(Cc = 55.3). Side (A) and cut open (B and C) views of the
connector are shown. The electrostatic potential surfaces (C)
were calculated with PBEQ-Solver (38).
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Figure 5.
Gp16 intersubunit disulfide bonding of the stopper region and
DNA ejection. (A) Structure of the gp16 stopper. Residues
mutated to cysteine are identified by colors. (B and C) Effect
of stopper amino acid substitutions to cysteine in monomeric
gp16 (B; no cross-linking) and in its dodecameric assembled form
found in viral particles (C; formation of covalently bound
subunit dimers (upper bands) in oxidation conditions that were
efficiently reduced with 4 mM DTT). (D) DNA ejection from
virions bearing gp16 mutations was assayed by a DNase protection
method that reveals the amount of DNA not released from viral
particles (19). Ejection was triggered by receptor addition
using a ratio of 1,250 YueB780 dimers (19) per virion in the
presence and in the absence of 4 mM DTT. All results were
reproduced in at least 3 independent experiments.
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