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PDBsum entry 2jaa
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Cell invasion
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PDB id
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2jaa
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References listed in PDB file
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Key reference
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Title
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Self-Chaperoning of the type III secretion system needle tip proteins ipad and bipd.
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Authors
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S.Johnson,
P.Roversi,
M.Espina,
A.Olive,
J.E.Deane,
S.Birket,
T.Field,
W.D.Picking,
A.J.Blocker,
E.E.Galyov,
W.L.Picking,
S.M.Lea.
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Ref.
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J Biol Chem, 2007,
282,
4035-4044.
[DOI no: ]
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PubMed id
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Abstract
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Bacteria expressing type III secretion systems (T3SS) have been responsible for
the deaths of millions worldwide, acting as key virulence elements in diseases
ranging from plague to typhoid fever. The T3SS is composed of a basal body,
which traverses both bacterial membranes, and an external needle through which
effector proteins are secreted. We report multiple crystal structures of two
proteins that sit at the tip of the needle and are essential for virulence: IpaD
from Shigella flexneri and BipD from Burkholderia pseudomallei. The structures
reveal that the N-terminal domains of the molecules are intramolecular
chaperones that prevent premature oligomerization, as well as sharing structural
homology with proteins involved in eukaryotic actin rearrangement. Crystal
packing has allowed us to construct a model for the tip complex that is
supported by mutations designed using the structure.
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Figure 4.
FIGURE 4. Consequences of removal of the N-terminal domain.
a, proteolytic sensitivity of the N-terminal domain of IpaD.
IpaD was incubated with trypsin at various ratios (w:w), and the
resulting digests were resolved on SDS-PAGE. Band 1 (24 kDa)
begins at residue 120 and Band 2 (20 kDa) at residue 138. b,
surface representation of IpaD[39-130] (left) and IpaD[131-322]
(right) with hydrophobic residues colored green and brown,
respectively. IpaD[39-130] is rotated through 180° along the
long axis relative to IpaD[131-322] to demonstrate the
complementary hydrophobic surfaces. The surface is presented as
transparent to allow visualization of the secondary structure.
c, analytical gel filtration chromatography (Superdex 200, HR
10/30) of IpaD before and after subtilisin treatment. Elution
volume of each species is noted along with the M[r] calculated
from SDS-PAGE. d, overlay of five structures of the IpaD
coiled-coil demonstrating the flexibility of the helices in the
absence of the N-terminal domain. The conformation of the coil
in the presence of the N-terminal domain is shown in green. The
C-terminal domain has been removed to aid clarity.
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Figure 5.
FIGURE 5. Oligomerization of IpaD. a, ribbon diagram of the
non-crystallographic dimer found in crystal form 2 (18).
Molecule A is shown in green and molecule B in blue. b, detailed
view of the dimer interaction site with side chains displayed,
colored as in a. Only structural elements that contribute to the
binding site are displayed for clarity. c, pentamer produced
using the non-crystallographic symmetry from crystal form 2. At
the top are ribbon representations and at the bottom surface
views. The panels on the left are related to the panels on the
right by a rotation of 90°.
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The above figures are
reprinted
from an Open Access publication published by the ASBMB:
J Biol Chem
(2007,
282,
4035-4044)
copyright 2007.
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