Type 1 and 5 secretion systems and associated toxins - Escherichia coli: Pathotypes and Principles of Pathogenesis - page 502

TABLE 16.1 Type 5 secreted proteins of E. coli —cont'd

Pathotypes
predominantly
associated with
the protein

Characterized
virulence
properties Protein Reference

EtpA,
EtpB

ETEC Adhesion to host

epithelial cells

( Fleckenstein et al.,
2006 )

OtpA,
OtpB

EHEC ( Choi et al., 2007 )

TAA

EibA-G UPEC Immunoglobulin

binding and serum
resistance

( Sandt and Hill,
2000, 2001 )

Saa EHEC Adhesion to Hep-2

cells, autoaggregation

( Paton et al., 2001 )

UpaG UPEC Adhesion to T24

cells, biofilm forma-
tion, autoaggregation,
adhesion to ECM

( Valle et al., 2008a )

5e

Intimin EPEC, EHEC Adhesion to eukary-

otic cells by binding
to Tir receptor

( Jerse et al., 1990 )

Antigen 43
The prototypical E. coli AT is Antigen 43 (Ag43). Found in nearly all E. coli
strains, Ag43 has the classic three-domain AT structure and functional proper-
ties common to many E. coli AT proteins; aggregation and biofilm formation
( Henderson et al., 1997; Hasman et al., 1999; Danese et al., 2000; Klemm et al.,
2004 ). The expression of Ag43 is phase variable, with switching rates of ~10 -3
per cell per generation due to the concerted actions of Dam-methylase (posi-
tive regulation) and OxyR (negative regulation) ( Henderson and Owen, 1999;
Waldron et al., 2002; Schembri et al., 2003a; Lim and van Oudenaarden, 2007 ).
Ag43 can be expressed on the E. coli cell surface in very high numbers (up to
50 000 copies per cell), resulting in some strains in a characteristic frizzy colony
morphology ( Henderson and Owen, 1999; Hasman et al., 2000 ).
The most distinctive phenotype of Ag43 is the protein's ability to medi-
ate aggregation which can be visualized macroscopically as flocculation and
settling of cells in static liquid suspensions. Ag43-mediated aggregation is a