Intimin is a

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

( 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 Shigatoxigenic ''Escherichia coli'' (STEC) and verotoxigenic ''E. coli'' (VTEC) are strains of the bacterium ''Escherichia coli'' that produce Shiga toxin (or verotoxin). Only a minority of the strains cause illness in humans. The ones that do ...

diarrhoea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

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

Type three secretion system Type three secretion system (often written Type III secretion system and abbreviated TTSS or T3SS, also called Injectisome) is a protein appendage found in several Gram-negative bacteria. In pathogenic bacteria, the needle-like structure is u ...

. 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

''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 a ...

of the

C-terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal 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 the protein is ...

domain Domain may refer to: Mathematics *Domain of a function, the set of input values for which the (total) function is defined ** Domain of definition of a partial function ** Natural domain of a partial function **Domain of holomorphy of a function * ...

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 ''Yersinia pseudotuberculosis'' is a Gram-negative bacterium that causes Far East scarlet-like fever in humans, who occasionally get infected zoonotically, most often through the food-borne route. Animals are also infected by ''Y. pseudotuber ...

'' and ''

Yersinia enterocolitica ''Yersinia enterocolitica'' is a Gram-negative, bacillus-shaped bacterium, belonging to the family Yersiniaceae. It is motile at temperatures of 22–29° C (72–84 °F), but becomes nonmotile at normal human body temperature. ''Y. enterocolit ...

'', 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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