Nature Structural Biology8, 1031 - 1036 (2001)
Published online: 29 October 2001; | doi:10.1038/nsb717
Structural and biochemical characterization of the type III secretion chaperones CesT and SigE
Yu Luo1, 2, Michela G. Bertero1, 2, Elizabeth A. Frey1, 3, Richard A. Pfuetzner1, Markus R. Wenk4, Louise Creagh3, Sandra L. Marcus3, Daniel Lim1, Frank Sicheri5, Cyril Kay6, Charles Haynes3, B. Brett Finlay1, 3
& Natalie C.J. Strynadka1
1
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver V6T 1Z3, Canada.
2
These authors contributed equally to this work.
3
Biotechnology Laboratory, University of British Columbia, Vancouver V6T 1Z3, Canada.
4
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
5
Department of Molecular and Medical Genetics, University of Toronto, Toronto M5G 1X5, Canada.
6
Protein Engineering Network of Centres of Excellence, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
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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