Tir (receptor)

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Tir (translocated intimin receptor) is an essential component in the binding of the pathogenic Escherichia coli strain EPEC (enteropathogenic E. coli) to the cells lining the small intestine. Tir is a receptor protein encoded by the espE gene which is located on the locus of enterocye effacement (LEE) pathogenicity island in EPEC strains. This receptor binds intimin upon translocation to enterocytes of the host cell.

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.