Transfer region of pO113 from enterohemorrhagic Escherichia coli: similarity with R64 and identification of a novel plasmid-encoded autotransporter, EpeA.
Enterohemorrhagic Escherichia coli (EHEC) is a prominent, food-borne cause of diarrhea, bloody diarrhea, and the hemolytic uremic syndrome in industrialized countries. Most strains of EHEC carry the locus for enterocyte effacement (LEE) pathogenicity island, but a proportion of isolates from patients with severe disease do not carry LEE and very little is known about virulence factors in these organisms. LEE-negative strains of EHEC typically express Shiga toxin 2 and carry a large plasmid that encodes the production of EHEC hemolysin. In this study, we determined the nucleotide sequence of the transfer region of pO113, the large hemolysin plasmid from LEE-negative EHEC O113:H21 (EH41). This 63.9-kb region showed a high degree of similarity with the transfer region of R64, and pO113 was capable of self-transmission at low frequencies. Unlike R64 and the related dot/icm system of Legionella pneumophila, however, pO113 was unable to mobilize RSF1010. In addition, the pO113 transfer region encoded a novel high-molecular-weight serine protease autotransporter of Enterobacteriaceae (SPATE) protein, termed EpeA. Like other SPATEs, EpeA exhibited protease activity and mucinase activity, but expression was not associated with a cytopathic effect on epithelial cells. Analysis of a second high-molecular-weight secreted protein revealed that pO113 also encodes EspP, a cytopathic SPATE identified previously in EHEC O157:H7. The nucleotide sequences encoding the predicted beta-domains of espP and epeA were identical and also shared significant homology with a third SPATE protein, EspI. Both espP and epeA were detected in several LEE-negative clinical isolates of EHEC and thus may contribute to the pathogenesis of this subset of EHEC.
Department of Microbiology, School of Biomedical Sciences, Monash University, Clayton 3800, Victoria, Australia.
Denisse L
DL
Leyton
Joan
J
Sloan
Rebecca E
RE
Hill
Steven
S
Doughty
Elizabeth L
EL
Hartland
D019453:Escherichia coli O157 / Q000235:genetics* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D006460:Hemolysin Proteins / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D010957:Plasmids; D011133:Polysaccharide-Lyases / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D013696:Temperature
D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C107189:EspP protein, E coli; D012697:Serine Endopeptidases; D011133:Polysaccharide-Lyases; C100002:hyaluronate lyase