title: Structural and biochemical characterization of the type III secretion chaperones CesT and SigE.
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.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver V6T 1Z3, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Luo
authors.forename: M G
authors.initials: MG
authors.lastname: Bertero
authors.forename: E A
authors.initials: EA
authors.lastname: Frey
authors.forename: R A
authors.initials: RA
authors.lastname: Pfuetzner
authors.forename: M R
authors.initials: MR
authors.lastname: Wenk
authors.forename: L
authors.initials: L
authors.lastname: Creagh
authors.forename: S L
authors.initials: SL
authors.lastname: Marcus
authors.forename: D
authors.initials: D
authors.lastname: Lim
authors.forename: F
authors.initials: F
authors.lastname: Sicheri
authors.forename: C
authors.initials: C
authors.lastname: Kay
authors.forename: C
authors.initials: C
authors.lastname: Haynes
authors.forename: B B
authors.initials: BB
authors.lastname: Finlay
authors.forename: N C
authors.initials: NC
authors.lastname: Strynadka
mesh_terms: 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
chemical_list: D001426:Bacterial Proteins; C122044:CesT protein, E coli; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D012997:Solvents