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PDBsum entry 1k3s
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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 biochemical characterization of the type III secretion chaperones cest and sige.
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Authors
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Y.Luo,
M.G.Bertero,
E.A.Frey,
R.A.Pfuetzner,
M.R.Wenk,
L.Creagh,
S.L.Marcus,
D.Lim,
F.Sicheri,
C.Kay,
C.Haynes,
B.B.Finlay,
N.C.Strynadka.
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Ref.
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Nat Struct Biol, 2001,
8,
1031-1036.
[DOI no: ]
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PubMed id
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Abstract
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Several Gram-negative bacterial pathogens have evolved a type III secretion
system to deliver virulence effector proteins directly into eukaryotic cells, a
process essential for disease. This specialized secretion process requires
customized chaperones specific for particular effector proteins. The crystal
structures of the enterohemorrhagic Escherichia coli O157:H7 Tir-specific
chaperone CesT and the Salmonella enterica SigD-specific chaperone SigE reveal a
common overall fold and formation of homodimers. Site-directed mutagenesis
suggests that variable, delocalized hydrophobic surfaces observed on the
chaperone homodimers are responsible for specific binding to a particular
effector protein. Isothermal titration calorimetry studies of Tir-CesT and
enzymatic activity profiles of SigD-SigE indicate that the effector proteins are
not globally unfolded in the presence of their cognate chaperones.
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Figure 1.
Figure 1. Electron density with MAD phases improved by solvent
modification. The stereo FOM-weighted F[o] maps are contoured
at 1.4  .
a, 2.8 Å map of CesT at the domain-swap interface. b, 1.9 Å map
of SigE at the dimeric interface.
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Figure 2.
Figure 2. Monomeric structures of a, CesT and b, SigE. c,
Structure-based sequence alignment of CesT (top) and SigE
(bottom). Helices are shaded blue; strands, green. Hydrophobic
residues exposed on the surface of the SigE or SigE-like CesT
homodimers are highlighted in red. The C-terminal amphipathic
helix predicted by sequence analysis to be a potential source of
hydrophobic residues for interaction with effector proteins4
packs with its hydrophobic face pointing into the buried
hydrophobic core of the protein in both CesT and SigE. Thus,
this region unlikely provides interactions with the effector
unless dramatic unfolding of the chaperone occurs upon complex
formation. (a,b), as well as Fig. 3a -c, were generated by
MOLSCRIPT34 and RASTER3D^35.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Biol
(2001,
8,
1031-1036)
copyright 2001.
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