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Infect. Immun., Feb 1995, 640-646, Vol 63, No. 2
C Wenneras, JR Neeser and AM Svennerholm
We have attempted to characterize the binding specificity of the coli
surface 3 (CS3) subcomponent of colonization factor antigen II of
enterotoxigenic Escherichia coli, by means of an immunoblot method in which
the binding of fimbriated bacteria to sodium dodecyl sulfate-
polyacrylamide gel electrophoresis-separated rabbit intestinal cell
membranes was evaluated. Isolated CS3 fibrillae as well as bacteria
expressing CS3 on their surface bound to several intestinal cell membrane
structures, i.e., structures present in the electrophoretic front and in
the 30- to 35-kDa range and, most prominently, 120- to 140- kDa structures.
Delipidization and protein digestion of the rabbit brush borders revealed
that CS3 bound to structures of a proteinaceous nature. Sodium
meta-periodate oxidation of the intestinal cell membranes abolished all
their CS3 binding activity, indicating that CS3 bound to carbohydrate
moieties of glycoproteins. The binding of CS3 to the separated intestinal
proteins could also be inhibited by preincubation with the lectin derived
from Maackia amurensis, indicating that CS3 bound to galactoproteins in the
rabbit intestine. Inhibition experiments using equimolar amounts of various
gangliosides demonstrated that GM1, asialo-GM1, and GM2 inhibited the
binding of CS3 equally well, whereas GM3 was not as effective. These
results suggested that the critical CS3 binding epitope consisted of the
carbohydrate sequence GalNAc beta 1-4Gal. This was supported by electron
microscopic experiments showing that this disaccharide, O linked to bovine
serum albumin via a spacer, localized around CS3-positive bacteria but not
at all around corresponding CS3-negative mutants. Furthermore, CS3-
expressing bacteria recognized this neoglycoprotein when it was immobilized
on nitrocellulose. The GalNAc beta 1-4Gal disaccharide has also been
implicated as a binding structure for other pathogenic bacteria such as
enteropathogenic E. coli and Pseudomonas aeruginosa.
Copyright © 1995, American Society for Microbiology
Binding of the fibrillar CS3 adhesin of enterotoxigenic Escherichia coli to rabbit intestinal glycoproteins is competitively prevented by GalNAc beta 1-4Gal-containing glycoconjugates
Department of Medical Microbiology and Immunology, University of Goteborg, Sweden.
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