Table 1 Summary of known characteristics of LEE-encoded genes and their associated proteins, with novel homology-based functional predictions. New names as suggested in body text of this article. Summary of effects on gene expression, type-III secretion and virulence in mice drawn from Deng et al [33]. Yeast two-hybrid results drawn from Creasey et al [145]. Predictions drawn from combination of homology data and cited works. T3S: involved in type-III secretion.

rorf1

+

+/+

EspD

YjiK

SdiA-regulated domain (NHL repeats)

SdiA-regulated?

espG

+

+/+

VirA

Translocated effector

ler

No expression

-/-

H-NS, StpA

Positive regulator

Might form heterodimers with H-NS, StpA

orf2 (escE)

-

Orf29

YscE, PscE, SsaE, CV2595, YPO0259

T3S

Interacts with C-terminus of SepL; Functionally important conserved residues can be identified by scrutiny of homologues

cesAB

± EspA, EspB

-/-

EspA, EspB

none

Chaperone for EspA and EspB

orf4

-

-/-

YPO0264, SsaK, CV2589

T3S

Functionally important conserved residues can be identified by scrutiny of homologues

orf5 (escL)

-

-/-

YscL, FliH

T3S

Binds to and regulates activity of ATPase EscN

escR

-

-/-

EscR, EscS, EscU, SepZ EspD

YscR, FliP

PF00813

T3S

escS

-

-/-

EscR, EspD

YscS, FliQ

PF01313

T3S

escT

-

-/-

YscT, FliR

PF01311

T3S

Physically associated in the basal body with EscU in a 1:1 ratio; C-terminus is cytoplasmic [158]

escU

-

-/-

EscrR, EscI, EspD

Yscu, FlhB

PF00771

T3S

Physically associated in the basal body with EscT in a 1:1 ratio [158]; cleaved at NPTH motif [159]; regulates substrate specificity of secretion system [160].

rorf3 (etgA)

±

±/±

EscI

lytic transglycosylase IagB, IpgF

Lytic transglycosylase needed to open gap in peptidoglycan for assembly of secretion system [58]; potential drug target

grIR

+

+/++

GrlR/GrlA

Bongori regulator

Negative regulator

Will work in concert with GrlA

grIA

No expression

-/-

GrlR

Bongori regulator, CaiF

Positive regulator

Will work in concert with GrlR

cesD

-/EspD

±/-

Other TPR chaperones

Chaperone for EspD

TPR chaperone [115]

escC

-

-/-

EscD

YscC, MxiD, InvG

T3S

Interacts with peptidoglycan [161], Dsb-dependent domain missing

sepD

-/Translocators

-/-

SepL

None

Switches translocator/effector secretion

Works in concert with SepL

escJ

-

-/-

YscJ, PrgK, FliF

PF01514

T3S

EscD and EscJ form ring-like structure in inner membrane [66, 162, 163]

rorf8 (escI)

-

-/-

EscU, rORF3

PrgJ, MxiI, YscI

T3S

Forms inner rod within base of needle complex [65, 68-70].

sepZ

+

+/±

EscR

None

Translocated effector

orf12

-

-/-

SsaM

T3S

Might play a role in switching translocator/effector secretion

escN

-

-/-

CesT, Tir [50]

YscN

T3S ATPAse

Forms hexameric complex

escV

-

-/-

LcrD, FlhA

PF00771

T3S

C-terminal cytoplasmic domain might play a role in gene regulation [164, 165].

orf15

-

-/-

None

T3S

orf16

±/Translocators

±/±

None

Secretion of translocators

FliK/YscP analogue?

sepQ (escQ)

-

-/-

YscQ, FliN

COG1887

T3S

Forms ring within basal body [56]; interacts with EscL [54]

espH

+

+/++

Translocated effector

cesF

±/EspF?

+/+

Chaperone for EspF

map

+

+/++

Translocated effector

tir

+

-/-

CesT Tir

Translocated effector

cesT

±/Tir

-/-

Map, EspF, Tir, CesT

Many

Chaperone for Tir

Possible regulatory role, by analogy with ExsC?

eae

+

-/-

Adhesin (intimin)

escD

-

-/-

YscD, PrgH

YscD: FHA and BON domains

T3S

EscD and EscJ form ring-like structure in inner membrane [66, 162, 163]; BON domains mediate binding to phospholipids; FHA domain mediates protein-protein interactions and signalling

sepL

-/Translocators

-/-

SepD

YopN, TyeA

Switches translocator/effector secretion

single protein mediating effects of YopN and TyeA; internal interaction between YopN- and TyeA-like moieties; also a translocated effector?

espA

+

-/-

CesAB

flagellin

Translocator

Half-flagellin model (see text); dimerizes before polymerizes; lacks D0 and D3 domains

espD

+

-/-

EspD, EscRSU, CesD, rORF1, SepZ

YopB etc

Translocator

espB

+

-/-

CesAB

YopD etc

Translocator

cesD2

±/EspD?

+/±

LcrR

Chaperone for EspD

LcrR will bind YopB

escF

-

-/-

YscF

Major needle component

orf29

-

-/-

Orf2

YPO0261, SsaI, H, CV2586

T3S

Functionally important conserved residues can be identified by scrutiny of homologues

espF

+

+/+

Translocated effector