Structural and biochemical characterization of the type III secretion chaperones CesT and SigE.
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.
Luo
Y
Y
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver V6T 1Z3, Canada.
Bertero
M G
MG
Frey
E A
EA
Pfuetzner
R A
RA
Wenk
M R
MR
Creagh
L
L
Marcus
S L
SL
Lim
D
D
Sicheri
F
F
Kay
C
C
Haynes
C
C
Finlay
B B
BB
Strynadka
N C
NC
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002151:Calorimetry; D018360:Crystallography, X-Ray; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D008027:Light; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D019779:Salmonella enterica / Q000737:chemistry*; D012542:Scattering, Radiation; D016415:Sequence Alignment; D012997:Solvents; D013379:Substrate Specificity; D014461:Ultracentrifugation
D001426:Bacterial Proteins; C122044:CesT protein, E coli; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D012997:Solvents