PDBsum entry 1k3s

Chaperone

PDB id: 1k3s

Contents

Protein chains

109 a.a.

Ligands

PO4

Waters ×50

PDB id:

1k3s

Name:

Chaperone

Title:

Type iii secretion chaperone sige

Structure:

Sige. Chain: a, b. Fragment: full length. Engineered: yes. Mutation: yes

Source:

Salmonella enterica. Organism_taxid: 28901. Strain: atcc14028s. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Biol. unit:

Dimer (from PQS)

Resolution:

1.90Å R-factor: 0.224 R-free: 0.272

Authors:

M.G.Bertero,Y.Luo,E.A.Frey,R.A.Pfuetzner,M.R.Wenk,L.Creagh, S.L.Marcus,D.Lim,B.B.Finlay,N.C.J.Strynadka

Key ref:

Y.Luo et al. (2001). Structural and biochemical characterization of the type III secretion chaperones CesT and SigE. Nat Struct Biol, 8, 1031-1036. PubMed id: 11685226 DOI: 10.1038/nsb717

Date:

03-Oct-01 Release date: 28-Nov-01

Protein chains

A0A0F6AZQ4  (A0A0F6AZQ4_SALT1) -  Chaperone protein from Salmonella typhimurium (strain 14028s / SGSC 2262)

Seq: 113 a.a.

Struc: 109 a.a.

DOI no: 10.1038/nsb717

Nat Struct Biol 8:1031-1036 (2001)

PubMed id: 11685226

Structural and biochemical characterization of the type III secretion chaperones CesT and SigE.

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.

ABSTRACT

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.

Selected figure(s)

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.

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.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nat Struct Biol (2001, 8, 1031-1036) copyright 2001.

Figures were selected by an automated process.