TABLE 1.
Ysc secretion apparatus
| Protein | Size (kDa) | Featuresa | Localization in bacteriaa | Role in Yop secretiona | Reference(s) |
|---|---|---|---|---|---|
| YscA | 3.8 | Hydrophobic C-terminal domain | Unknown | − | 228, 296 |
| YscB | 15.4 | Unknown | NT | 228 | |
| YscC | 67.1 | Signal sequence of 26 residues; member of the secretin family; forms pores of 200 Å with a central channel of 50 Å | OM | + | 194, 228 |
| YscD | 46.7 | Hydrophobic domain (aa 120–130) | IM | + | 228, 265 |
| YscE | 7.4 | Hydrophobic C-terminal domain | Unknown | + | 8, 228 |
| YscF | 9.4 | Unknown | + | 8, 228 | |
| YscG | 12.9 | Hydrophobic N-terminal domain | C/M | + | 8, 228, 265 |
| YopR | 18.3 | Encoded by yscH | Secreted | − | 8, 228 |
| YscI | 12.6 | Unknown | + | 8, 228 | |
| YscJ | 27.0 | Lipoprotein; hydrophobic C-terminal domain followed by 3 positively charged residues; previously called YlpB | Unknown | + | 8, 64, 228 |
| YscK | 23.9 | One hydrophobic domain | Unknown | + | 8, 228 |
| YscL | 24.9 | Unknown | + | 228, 326 | |
| YscM1/LcrQ | 12.3 | Resembles YscM2 and YopH | Secreted | − | 8, 228, 327 |
| YscN | 47.8 | Contains Walker box A and B; putative ATPase | IM/C | + | 24, 93, 375 |
| YscO | 19.0 | Secreted | + | 24, 93, 252 | |
| YscP | 50.4 | Secreted | + | 24, 93, 252a, 326a | |
| YscQ | 34.4 | Unknown | + | 24, 93 | |
| YscR | 24.4 | Four transmembrane domains and a large central cytoplasmic region | IM | + | 24, 93 |
| YscS | 9.6 | Two putative transmembrane domains | Unknown (probably IM) | + | 24, 93, 261 |
| YscT | 28.4 | Six putative transmembrane domains | Unknown (probably IM) | NT | 24, 93 |
| YscU | 40.3 | Four transmembrane domains at the N terminus with a large cytoplasmic C-terminal region | IM | + | 9, 24, 93 |
| YscX | 13.6 | Unknown | + | 170a | |
| YscY | 13.1 | Unknown | + | 170a | |
| LcrD/YscV | 77.8 | Eight potential transmembrane domains; hydrophobic N-terminal half; hydrophilic C terminus predicted to protrude into the cytoplasm | IM | + | 263 |
| VirG/YscW | 14.6 | Lipoprotein ancillary to YscC secretin | Probably OM | + (YopB, YopD, LcrV) | 7 |
a
IM, inner membrane; OM, outer membrane; C, cytosolic; M, membrane-associated protein; NT, not tested; +, required for secretion; −, not required for secretion; aa, amino acids.