Tir (receptor)

Tir (translocated intimin receptor) is an essential component in the adherence of the enteropathogenic Escherichia coli (EPEC) and enterohemorraghic Escherichia coli (EHEC) to the cells lining the small intestine. To aid attachment, both EPEC and EHEC possess the ability to reorganise the host cell actin cytoskeleton via the secretion of virulence factors. These factors are secreted directly into the cells using a Type three secretion system. One of the virulence factors secreted is the Translocated Intimin Receptor (Tir). Tir is a receptor protein encoded by the espE gene which is located on the locus of enterocyte effacement (LEE) pathogenicity island in EPEC strains. It is secreted into the host cell membranes and acts as a receptor for intimin which is found on the bacterial surface. Once Tir binds intimin, the bacterium is attached to the enterocyte surface.^[1]^[2]

Tir is also a receptor tyrosine kinase (RTK) that initiates its intimate adherence by inserting a hairpin orientation in the intestinal cell membrane to enable tight binding to intimin on the bacterial cell outer membrane. Upon phosphorylation, Tir activates condensation and polymerization of actin filaments under the bacterial cell to form a pedestal-like structure.^[1]

References

^ ^a ^b Stevens, J.; et al. (2006). "Actin-dependent movement of bacterial pathogens". Nature Reviews Microbiology. 4 (2): 91–101. doi:10.1038/nrmicro1320. PMID 16415925.
^ Batchelor, M.; et al. (2000). "Structural basis for recognition of the translocated intimin receptor (Tir) by intimin from enteropathogenic Escherichia coli". The EMBO Journal. 19 (11): 2452–2464. doi:10.1093/emboj/19.11.2452. PMC 212744. PMID 10835344.

[pmid16415925-1] Stevens, J.; et al. (2006). "Actin-dependent movement of bacterial pathogens". Nature Reviews Microbiology. 4 (2): 91–101. doi:10.1038/nrmicro1320. PMID 16415925.

[pmid10835344-2] Batchelor, M.; et al. (2000). "Structural basis for recognition of the translocated intimin receptor (Tir) by intimin from enteropathogenic Escherichia coli". The EMBO Journal. 19 (11): 2452–2464. doi:10.1093/emboj/19.11.2452. PMC 212744. PMID 10835344.

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v t e Enzymes
Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Diffusion-limited enzyme Cofactor Enzyme catalysis
Regulation	Allosteric regulation Cooperativity Enzyme inhibitor Enzyme activator
Classification	EC number Enzyme superfamily Enzyme family List of enzymes
Kinetics	Enzyme kinetics Eadie–Hofstee diagram Hanes–Woolf plot Lineweaver–Burk plot Michaelis–Menten kinetics
Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list) EC7 Translocases (list)