Table 1.

Ysc secretion apparatus

ProteinSize (kDa)FeaturesaLocalization in bacteriaaRole in Yop secretionaReference(s)
YscA3.8Hydrophobic C-terminal domainUnknown228, 296
YscB15.4UnknownNT228
YscC67.1Signal sequence of 26 residues; member of the secretin family; forms pores of 200 Å with a central channel of 50 ÅOM+194, 228
YscD46.7Hydrophobic domain (aa 120–130)IM+228, 265
YscE7.4Hydrophobic C-terminal domainUnknown+8, 228
YscF9.4Unknown+8, 228
YscG12.9Hydrophobic N-terminal domainC/M+8, 228, 265
YopR18.3Encoded byyscHSecreted8, 228
YscI12.6Unknown+8, 228
YscJ27.0Lipoprotein; hydrophobic C-terminal domain followed by 3 positively charged residues; previously called YlpBUnknown+8, 64, 228
YscK23.9One hydrophobic domainUnknown+8, 228
YscL24.9Unknown+228, 326
YscM1/LcrQ12.3Resembles YscM2 and YopHSecreted8, 228, 327
YscN47.8Contains Walker box A and B; putative ATPaseIM/C+24, 93, 375
YscO19.0Secreted+24, 93, 252
YscP50.4Secreted+24, 93, 252a, 326a
YscQ34.4Unknown+24, 93
YscR24.4Four transmembrane domains and a large central cytoplasmic regionIM+24, 93
YscS9.6Two putative transmembrane domainsUnknown (probably IM)+24, 93, 261
YscT28.4Six putative transmembrane domainsUnknown (probably IM)NT24, 93
YscU40.3Four transmembrane domains at the N terminus with a large cytoplasmic C-terminal regionIM+9, 24, 93
YscX13.6Unknown+170a
YscY13.1Unknown+170a
LcrD/YscV77.8Eight potential transmembrane domains; hydrophobic N-terminal half; hydrophilic C terminus predicted to protrude into the cytoplasmIM+263
VirG/YscW14.6Lipoprotein ancillary to YscC secretinProbably 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.