Identification, characterization, and nucleotide sequence of the F17-G gene, which determines receptor binding of Escherichia coli F17 fimbriae

Abstract

Enterotoxigenic Escherichia coli strains express fimbriae which mediate binding to intestinal mucosal cells. The F17 fimbriae mediate binding to N-acetylglucosamine-containing receptors present on calf intestinal mucosal cells. These fimbriae consist of F17-A subunit peptides. Analysis of the F17 gene cluster indicated that at least the F17-A, F17-C, F17-D, and F17-G genes are indispensable to obtain adhesive F17 fimbriae (unpublished data). Genetic evidence is presented that the F17-G protein, a minor fimbrial component, is required for the binding of the F17 fimbriae to the intestinal villi. The F17-G gene was cloned and sequenced. An open reading frame of 1,032 bp encoding a polypeptide of 344 amino acids, starting with a signal sequence of 22 residues, was localized. The F17-G mutant strain produced F17 fimbriae which were morphologically identical to the fimbriae purified from strains which contained the intact F17 gene cluster. However, this F17-G mutant could no longer adhere to calf villi. The F17-G locus was shown to act in trans: transformation of the F17-G mutant strain, still expressing the genes F17-A, F17-C, and F17-D, with a vector expressing the F17-G gene restored the binding activity of this mutant strain.

The Escherichia coli G-fimbrial lectin protein participates both in fimbrial biogenesis and in recognition of the receptor N-acetyl-D-glucosamine

“…The predicted amino acid sequence of GafD appeared to be closely related to those of the F17-G and F17b-G fimbrial proteins of enterotoxigenic and invasive E. coli ( Fig. 5) (24,29) but distinct from those of the F17A and GafA G-fimbrial subunit proteins (25,26,32). Interestingly, all amino acid substitutions observed for GafD and F17-G and F17b-G were located in the N-terminal halves of the respective proteins (Fig.…”

“…Bacteria expressing these fimbriae adhere to intestinal brush borders, and this attachment can be inhibited with Nacetyl-D-glucosamine (23,24). A human pyelonephritogenic E. coli isolate possessing a related adhesion phenotype has also been documented (39).…”

“…The closely related F17 and F17b fimbriae are present on bovine enteropathogenic and septicemic E. coli strains (23)(24)(25)(26)29). Bacteria expressing these fimbriae adhere to intestinal brush borders, and this attachment can be inhibited with Nacetyl-D-glucosamine (23,24).…”

Pilins of fimbrial adhesins of different member species of enterobacteriaceae are structurally similar to the C‐terminal half of adhesin proteins

“…Adhesin proteins, generally composed of 260 to 340 amino acid residues, contain two Cys-Cys loops in similar positions and share homology (20-40%) sequence, indicating an apparent conservation in overall molecular structure. Although the adhesins are about twice the size of other fimbrial proteins, significant sequence agreement between pilins and the C-terminal half of adhesins has been reported [9,11], but whether or not adhesins and pilins support an overall homology in structure is not known.…”

“…Proteins corresponding in size and function to the E. eoli type I adhesin (FimH) have been identified in various fimbriae expressed by different member species of the family Enterobacteriaceae [8][9][10][11][12]. Adhesin proteins, generally composed of 260 to 340 amino acid residues, contain two Cys-Cys loops in similar positions and share homology (20-40%) sequence, indicating an apparent conservation in overall molecular structure.…”