Type III secretion system inner membrane P protein (IPR005838)

Short name: T3SS_IM_P

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 [PMID: 8969244]. 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. 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 [PMID: 10334981] 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 [PMID: 10564516]. However, while the latter forms a ring structure to allow secretion of flagellin and is an integral part of the flagellum itself [PMID: 10564516], type III subunits in the outer membrane translocate secreted proteins through a channel-like structure. It is believed that the family of type III inner membrane proteins are used as structural moieties in a complex with several other subunits [PMID: 9618447], including the ATPase necessary for driving the secretion system.

One such set of inner membrane proteins, termed "P" here for nomenclature purposes, includes the Salmonella and Shigella SpaP, the Yersinia YscR, the Erwinia HrcR, and the Xanthamonas Pro2 genes [PMID: 9618447], as well as several FliP flagellar biosynthesis genes [PMID: 10564516]. FliP is an ~30Kd protein containing three or four transmembrane (TM) regions.

GO terms

Biological Process

GO:0009306 protein secretion

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0016020 membrane

Contributing signatures

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