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Volume 2, Number 4—October 1996


Molecular Mechanisms of Bacterial Virulence: Type III Secretion and Pathogenicity Islands

Joan Mecsas and Evelyn J. Strauss
Author affiliations: Stanford University School of Medicine, Stanford, California

Main Article

Table 1

Function and location of components in Type III systemsa

Yersinia (p)b S. typhimurium
S. flexneri (p) EPEC 
(c) Flagellac (c) Plantd (c) Possible Functiond Possible Cellular Locationf Reference
SPI I(c) SPI II(c)
YscN SpaL orf1 MxiB SepB FliI HrpE ATPase cytoplasm, associated with inner membrane (I.M.) 8, 43, 63
LcrD InvA orf9 MxiA SepA FlhA HrpO structural/ regulatory I.M. 28, 43, 63
YscR SpaP orf5 Spa24 FliP HrpT structural I.M. 8, 43
YscS SpaQ orf6 Spa9 FliQ HrpU 28, 43
YscT SpaR orf7 Spa40 FliR HrpC 8, 43
YscU SpaS orf8 Spa40 FhlB HrpN 8, 43, 63
YscC InvG orf11 MxiD SepC HrpA structural/channel forming outer membrane (O.M.) 28, 43, 63
YscJ PrgK orf10 MxiJ SepD FliF HrpI lipoprotein/ structural O.M. 8, 28, 43, 63
VirG 52
YscD essential, but unknown I.M. 48
YscE unknown 51
YscF PrgI MxiH needed for YopB and D secretion 28, 51
YscG essential, butunknown equally distributed between membrane and soluble fractions 48
YscI unknown 51
YscK 51
YscL HrpF 8
YscO SpaM orf2 Spa13 unknown 12, 28, 43
YscP SpaN orf3 Spa32 12, 28, 43
YscQ SpaO orf4 Spa33 FliN HrpQ SpaO needed for secretion of Sips (see below) Spa O: secreted 8, 28, 43
YopB SipB IpaB homology to pore forming toxins/delivery of effector moleculesto host cells secreted/targeted to host cell 26, 28, 55
YopD delivery of effector molecules to host cells secreted 55
SipD IpaD secreted 26
SycD SicA IpgC chaperone for YopB and D/ IpaB and IpaC in Shigella cytoplasm 56
SycE chaperone for YopE 56
SycH chaperone for YopH 56
YopN InvE MxiC regulatory: cell-contact sensing pathway O.M./secreted 28
LcrG cytosol/I.M. 59, S. Straley pers. comm.
LcrQ regulatory cytoplasm/secreted 54
VirF InvF MxiE HrpB regulatory:temperature cytoplasm 28
YopE effector molecule:depolymerizes actin antiphagocytic host cell 27
YopH effector molecule: tyrosine phosphatase anti-phagocytic 36
SipC IpaC effector molecule: induces entry into epithelial cells secreted 17, 28
EspB (EaeB) effector molecule: induces AE lesions 33, 63

aListed are names of proteins in type III secretion systems
bp-proteins are encoded by genes on a plasmid; c-proteins are encoded by genes on the chromosome.
cProtein names are those from the S. Typhimurium flagella; for list of flagellar protein names from other bacteria, see ref. 23.
dProtein names are those from the plant pathogen Pseudomonas solanacearum; for a list of components of type III secretion systems in other plant pathogens, see ref. 8.
eThese are the possible functions for these factors in Yersinia, unless noted.
fThese are the possible locations for these factors in Yersinia, unless noted.

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