Intimin and its translocated intimin receptor (Tir) are bacterial proteins that mediate adhesion between mammalian cells and attaching and effacing (A/E) pathogens. A unique and essential feature of A/E bacterial pathogens is the formation of actin-rich pedestals beneath the intimately adherent bacteria and localised destruction of the intestinal brush border. The bacterial outer membrane adhesin, intimin, is necessary for the production of the A/E lesion and diarrhoea. The A/E bacteria translocate their own receptor for intimin, Tir, into the membrane of mammalian cells using the type III secretion system. The translocated Tir triggers additional host signalling events and actin nucleation, which are essential for lesion formation [1]. This family represents the Tir C-terminal domain which has been reported to bind uninfected host cells and beta-1 integrins although the role of intimin binding to integrins is unclear. This intimin C-terminal domain has also been shown to be sufficient for Tir recognition [2].

1: Crystal structure of enteropathogenic Escherichia coli intimin-receptor complex. Luo Y, Frey EA, Pfuetzner RA, Creagh AL, Knoechel DG, Haynes CA, Finlay BB, Strynadka NC; Nature 2000;405:1073-1077. PMID:10890451

2: Identification of the intimin-binding domain of Tir of enteropathogenic Escherichia coli. de Grado M, Abe A, Gauthier A, Steele-Mortimer O, DeVinney R, Finlay BB; Cell Microbiol 1999;1:7-17. PMID:11207537