Type II secretory pathway for surface secretion of DraD invasin from the uropathogenic Escherichia coli Dr+ strain.
The virulence of the uropathogenic Escherichia coli Dr(+) IH11128 strain is associated with the presence of Dr fimbrial structures and a DraD invasin which can act as a fimbrial capping domain at the bacterial cell surface. However, a recent study suggests that the DraD protein is surface exposed in two forms: fimbria associated and fimbria nonassociated (prone to interaction with the N-terminal extension of the DraE protein located on the fimbrial tip). The actual mechanism of DraD surface secretion is presently unknown. We identified a previously unrecognized type II secretory pathway (secreton) in the uropathogenic E. coli Dr(+) strain which is well conserved among gram-negative bacteria and used mainly for secretion of virulence determinants. An active secreton is composed of 12 to 15 different proteins, among which GspD functions as an outer-membrane channel to permit extrusion of proteins in a folded state. Therefore, we inactivated the pathway by inserting the group II intron into a gspD gene of the type II secretion machinery by site-specific recombination. DraD secretion by the E. coli Dr(+) and gspD mutant strains was determined by immunofluorescence microscopy (with antibodies raised against DraD) and an assay of cell binding between bacteria and HeLa cells. The specificity of DraD-mediated bacterial binding for the integrin receptor was confirmed by examination of the adhesion of DraD-coated beads to HeLa cells in the presence and absence of alpha(5)beta(1) monoclonal antibodies. The investigations that we performed showed that type II secretion in E. coli Dr(+) strains leads to DraD translocation at the bacterial cell surfaces.
Zalewska-Piatek
Beata
B
Department of Microbiology, Gdańsk University of Technology, ul G Narutowicza 11/12, 80-952 Gdańsk, Poland. beatazalewska1@o2.pl
Bury
Katarzyna
K
Piatek
Rafal
R
Bruzdziak
Piotr
P
Kur
Józef
J
D001422:Bacterial Adhesion; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry; D004847:Epithelial Cells / Q000382:microbiology; D004926:Escherichia coli / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000378:metabolism*; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D016254:Mutagenesis, Insertional; D021381:Protein Transport; D037521:Virulence Factors / Q000378:metabolism*
D002352:Carrier Proteins; C530426:DraD invasin, E coli; D029968:Escherichia coli Proteins; D037521:Virulence Factors; D036781:Fimbriae Proteins