A large number of bacterial pathogens, including Shigella, Salmonella, Bordetella, Pseudomonas, and pathogenic E. coli that are pathogenic for humans, other animals including insects or nematodes, and plants are equipped with a special protein- export apparatus called a type III secretion system (TTSS) or an injectisome. The injectisome is a highly sophisticated nanomachine that has specifically evolved to allow bacteria to deliver proteins into eukaryotic cells. The TTSS enables these pathogens to inject virulence proteins (known as effectors) directly into the cytoplasm of the eukaryotic host cells they infect. Many of these type III translocated effectors mimic eukaryotic factors and are capable of subverting key host cellular processes to the benefit of the pathogen during infection. Over the past decade, significant progress has been made in understanding the structure, assembly and the mode of operation of TTSS. The cytosolic components, the principal structural building proteins of the injectisome, from the basal body embedded in the inner and outer bacterial membrane to the tip of the needle protruding from the cell surface, have been extensively characterized. Virulence factors (effectors, needle proteins and translocators) form tight complexes with cognate chaperones in the cytosol and are subsequently targeted specifically to an ATPase protein located at the base of the injectisome. Powered by ATP, the effector is then translocated through the needle and is secreted in the eukaryotic cell. Fundamental questions about the functional mechanisms underpinning these processes remain unaddressed. We propose to use an integrated approach combining structural, dynamic, thermodynamic, kinetic, biochemical and in vitro and in vivo functional assays to provide insight into the early events of the secretion process that involve the recognition and binding of virulence factors (effectors and translocators) by cognate chaperones and the targeting of these substrates to the ATPase. We have extensively characterized over the last 3 years TTS protein components from the enteropathogenic Escherichia coli (EPEC), a prototype for TTSS and the major cause of infantile diarrhea and child mortality worldwide.
The specific aims are designed to provide atomic-resolution insight into (i) the mechanisms of specific interaction between TTS chaperones and virulence factors, (ii) the structural and dynamic properties of the ATPase, (iii) the """"""""recognition"""""""" or """"""""secretion"""""""" signal, and (iv) the specific targeting of chaperone-substrate complexes to the ATPase.

Public Health Relevance

Type III secretion system (TTSS) is encoded by many bacterial pathogens, including Shigella, Salmonella, Bordetella, Pseudomonas, and pathogenic E. coli that are pathogenic for humans and cause diseases such as plague, typhoid fever, bacterial dysentery and common food poisoning.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-BCMB-B (02))
Program Officer
Baqar, Shahida
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Rutgers University
Schools of Arts and Sciences
New Brunswick
United States
Zip Code
Xing, Qiong; Shi, Ke; Portaliou, Athina et al. (2018) Structures of chaperone-substrate complexes docked onto the export gate in a type III secretion system. Nat Commun 9:1773
Portaliou, Athina G; Tsolis, Konstantinos C; Loos, Maria S et al. (2017) Hierarchical protein targeting and secretion is controlled by an affinity switch in the type III secretion system of enteropathogenic Escherichia coli. EMBO J 36:3517-3531
Xia, Youlin; Rossi, Paolo; Tonelli, Marco et al. (2017) Optimization of 1H decoupling eliminates sideband artifacts in 3D TROSY-based triple resonance experiments. J Biomol NMR 69:45-52
Monneau, Yoan R; Rossi, Paolo; Bhaumik, Anusarka et al. (2017) Automatic methyl assignment in large proteins by the MAGIC algorithm. J Biomol NMR 69:215-227
Xia, Youlin; Rossi, Paolo; Subrahmanian, Manu V et al. (2017) Enhancing the sensitivity of multidimensional NMR experiments by using triply-compensated ? pulses. J Biomol NMR 69:237-243
Monneau, Yoan R; Ishida, Yojiro; Rossi, Paolo et al. (2016) Exploiting E. coli auxotrophs for leucine, valine, and threonine specific methyl labeling of large proteins for NMR applications. J Biomol NMR 65:99-108
Khanra, Nandish; Rossi, Paolo; Economou, Anastassios et al. (2016) Recognition and targeting mechanisms by chaperones in flagellum assembly and operation. Proc Natl Acad Sci U S A 113:9798-803
Rossi, Paolo; Xia, Youlin; Khanra, Nandish et al. (2016) 15N and 13C- SOFAST-HMQC editing enhances 3D-NOESY sensitivity in highly deuterated, selectively [1H,13C]-labeled proteins. J Biomol NMR 66:259-271
Chen, Li; Ai, Xuanjun; Portaliou, Athina G et al. (2013) Substrate-activated conformational switch on chaperones encodes a targeting signal in type III secretion. Cell Rep 3:709-15
Zuiderweg, Erik R P; Bagai, Ireena; Rossi, Paolo et al. (2013) EZ-ASSIGN, a program for exhaustive NMR chemical shift assignments of large proteins from complete or incomplete triple-resonance data. J Biomol NMR 57:179-91

Showing the most recent 10 out of 12 publications