Intimin/invasin bacterial adhesion mediator protein (IPR003535)

Short name: Intimin/invasin_bac

Overlapping homologous superfamilies

Family relationships



Secretion of virulence factors in Gram-negative bacteria involves transportation of the protein across two membranes to reach the cell exterior. There have been four secretion systems described in animal enteropathogens, such as Salmonella and Yersinia, with further sequence similarities in plant pathogens like Ralstonia and Erwinia [PMID: 9618447].

The type III secretion system is of great interest, as it is used to transport virulence factors from the pathogen directly into the host cell and is only triggered when the bacterium comes into close contact with the host. The protein subunits of the system are very similar to those of bacterial flagellar biosynthesis. However, while the latter forms a ring structure to allow secretion of flagellin and is an integral part of the flagellum itself [PMID: 9618447], type III subunits in the outer membrane translocate secreted proteins through a channel-like structure.

Exotoxins secreted by the type III system do not possess a secretion signal, and are considered unique for this reason [PMID: 9618447]. Enteropathogenic and entero- haemorrhagic Escherichia coli secrete the bacterial adhesion mediation molecule intimin [PMID: 10835344], which targets the translocated intimin receptor, Tir. Tir is secreted by the bacteria and is embedded in the target cell's plasma membrane [PMID: 10835344]. This facilitates bacterial cell attachment to the host.

The crystal structure of an enteropathogenic E. coli intimin C-terminal fragment has been determined to 1.9A resolution. The structure has also been resolved in complex with the Tir intimin-binding domain, giving insight into the molecular mechanisms of adhesion in attaching and effacing pathogens [PMID: 10890451].

Invasin is a protein that allows enteric bacteria to penetrate cultured mammalian cells [PMID: 3304658]. The entry of invasin in the cell is mediated by binding several beta-1 chain integrins [PMID: 10514372].

GO terms

Biological Process

GO:0007155 cell adhesion

Molecular Function

No terms assigned in this category.

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.