Intimin is a

virulence factor Virulence factors (preferably known as pathogenicity factors or effectors in botany) are cellular structures, molecules and regulatory systems that enable microbial pathogens (bacteria, viruses, fungi, and protozoa) to achieve the following: * c ...

( adhesin) of EPEC (''e.g.'' ''E. coli'' O127:H6) and EHEC (''e.g. E. coli'' O157:H7) '' E. coli'' strains. It is an attaching and effacing (A/E) protein, which with other virulence factors is necessary and responsible for enteropathogenic and enterohaemorrhagic

diarrhoea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

. Intimin is expressed on the bacterial cell surface where it can bind to its receptor Tir (Translocated intimin receptor). Tir, and over 25 other bacterial proteins are secreted from attaching and effacing ''E. coli'' directly into the cytoplasm of intestinal epithelial cells by a

Type three secretion system The type III secretion system (T3SS or TTSS) is one of the bacterial secretion systems used by bacteria to secretion, secrete their Bacterial effector protein, effector proteins into the host's cells to promote virulence and Colonisation (biology ...

. Once within the cytoplasm of the host cell, Tir is inserted into the plasma membrane, allowing surface exposure and intimin binding. Tir-intimin interaction mediates tight binding of enteropathogenic and enterohaemorrhagic ''E.coli'' to the intestinal epithelia, resulting in the formation of effacing lesions on intestinal epithelia. The

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

of the

C-terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, carboxy tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When t ...

domain has been solved and shown to have a C-lectin type of structure. It is the C-terminal domain that mediates attachment to Tir. It is a 94 kDa outer membrane protein encoded by ''eae''A gene in the locus of enterocyte effacement (LEE), a 35-Kb pathogenicity island. Mutations in the ''eaeA'' gene result in loss of ability to cause A/E lesions, and is required for full virulence in infected volunteers and animal models. The N-terminal domains of intimin from A/E lesion forming pathogens have high homology with each other and to invasin from '' Yersinia pseudotuberculosis'' and '' Yersinia enterocolitica'', whereas the C-terminal domains show less homology. Antibodies to intimin are present in: # Immune colostrum from mothers in EPEC endemic areas # The serum of EPEC/EHEC infected children and EPEC infected volunteers # Secretions of ''Citrobacter rodentium'' infected mice.

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