TABLE 2.
Proteins secreted by the SPI1 type III secretion system
| Protein | Host cell localizationa | Functionb | Homologuesc |
|---|---|---|---|
| SipA | Surface | NDd | IpaA (Shigella) |
| SipB | Intracellular | Translocation? Apoptosis? | IpaB (Shigella), EspD (EPECe), EspB (EHECe), Pep/PopB (Pseudomonas aeruginosa) |
| SipC | Intracellular | Translocation? | IpaC (Shigella) |
| SipD | Extracellular | Translocation? | IpaD (Shigella) |
| InvJ/SpaN | ND | Secretion | SpaN (Shigella) |
| SpaO | ND | Secretion | SpaO (Shigella); YscQ (Yersinia); FliNf |
| SptP | Intracellular | Cytoskeletal disruption; splenic colonization | YopE, ExoS (N-term.); YopH (C-term.) |
| SopE | Intracellular | Cytoskeletal reorganization; invasion | None identified |
| SigD/SopB | Intracellular | Invasion; transepithelial signaling of PMNs | IpgD (Shigella) |
| AvrA | Intracellular | ND | YopJ/YopP (Yersinia); AvrAxc (Xanthamonas) |
a
Localization of the secreted protein with respect to the eucaryotic host cell.
b
? indicates that the location of these proteins with respect to the host cell has not been determined.
c
Homologues listed have significant sequence and/or functional similarity to the respective Salmonella protein.
d
ND, not determined.
e
EHEC, enterohemorrhagic E. coli; EPEC, enteropathogenic E. coli.
f
FliN, “flagellar motor switch protein” from E. coli, S. typhimurium, Caulobacter crescentus, and several other gram-negative bacteria.