F17G/GafD

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== Progress toward understanding this GBP paradigm ==
== Progress toward understanding this GBP paradigm ==
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This section documents what is currently known about F17G/GafD, its carbohydrate ligand(s), and how they interact to mediate cell communication.
=== Carbohydrate ligands ===
=== Carbohydrate ligands ===
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=== Cellular expression of GBP and ligands ===
=== Cellular expression of GBP and ligands ===
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F17G adhesins are expressed on enterotoxigenic E. coli infecting neonatal lambs, calves, and goat kids.  
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F17G adhesins are expressed on enterotoxigenic E. coli infecting neonatal lambs, calves, and goat kids.
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The F17G ligand GlcNAcb1,3Gal occurs universally but mostly internally in the sequence of poly-lactosaminyl glycans and blood group antigens.  
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The F17G ligand GlcNAcb1,3Gal occurs universally but mostly internally in the sequence of poly-lactosaminyl glycans and blood group antigens.
These glycan structures are widely expressed on mamalian cell surfaces .
These glycan structures are widely expressed on mamalian cell surfaces .

Revision as of 17:40, 6 August 2010

The F17-G (GafD) adhesin at the tip of flexible F17 fimbriae of enterotoxigenic Escherichia coli mediates binding to N-acetyl-β-D-glucosamine-presenting receptors on the microvilli of the intestinal epithelium of ruminants, leading to diarrhea or septicaemia. F17-G belong to two-domain adhesins (TDA)s consisting of a pilin domain and a lectin domain, both having an Ig-fold joined via a short interdomain linker [1][2]. Related adhesins have been characterized in enteropathogenic E. coli ( FedF on F18 fimbriae[3] and CfaE on CFA/I pili[4]) ) and uropathogenic ones (FimH on type 1 fimbriae[5] and PapG on P-pili[6]). Fimbrial adhesins from other organisms, such as CupB6 from Pseudomonas aeruginosa are also investigated. All share the immunoglobulin-like fold of the two structural components, despite lack of any sequence identity and diversity in carbohydrate specificity and binding site, and the corresponding pili are assembled by the chaperone-usher pathway[7][8]. The paradigm is unique among TAD for his specificity toward GlcNAc. The binding site is located laterally and not at the tip of the pili, therefore the long and flexible F17 fimbriae could intrude between the microvilli of the epithelium, with the binding site of the lectin domain interacting laterally with GlcNAc-containing receptors. Five naturally occurring variants, differing in 1-18 amino acids of the adhesion domain have been identified[9].

Contents

CFG Participating Investigators contributing to the understanding of this paradigm

This is an emerging field of investigation and contributions arose from a small number of CFG Participating Investigators (PIs). These include: Esther Bullit, Eric Cox, Anne Imberty, Remy Loris, James Nataro

Progress toward understanding this GBP paradigm

This section documents what is currently known about F17G/GafD, its carbohydrate ligand(s), and how they interact to mediate cell communication.

Carbohydrate ligands

The F17G adhesin is most specific for the disaccharide GlcNAcb1,3Gal that can be recognised as a terminal or internal sequence in bovine glycophorin [10]:
File:carbSynthe_0691_D000.jpg
The branched form gives a closely similar fluorescent signal:
File:carbSynthe_0897_D000.jpg
The presence of the b1,3 linkage of N-acetyl glucosamine to galactose enhances the affinity for F17G at least 2-fold, compared to the monosaccharide N-acetyl glucosamine, as validated using surface plasmon resonance measurements. Second best binders are the b1,4 and b1,6 galactose linked disaccharides, whereas chitobiose, that is also a characterized inhibitor of F17G-mediated bacterial adhesion, is clearly lagging behind. F17G can thus be ranked under glycan binding proteins that display high selectivity.

Cellular expression of GBP and ligands

F17G adhesins are expressed on enterotoxigenic E. coli infecting neonatal lambs, calves, and goat kids. The F17G ligand GlcNAcb1,3Gal occurs universally but mostly internally in the sequence of poly-lactosaminyl glycans and blood group antigens. These glycan structures are widely expressed on mamalian cell surfaces .

Biosynthesis of ligands


F17-fimbriated E. coli predominantly colonize neonatal animals, but also are a major causal agent (55%) of mastitis in bovines [11]. Congruent with the glycans recognized by F17G on the printed array versions 2.1 and 4.1, the N-acetyl glucosamine residue of GlcNAcb1,3Gal may be unsubstituted at the early life stage of calves, that are at the same time protected from bacterial infections by glycans secreted in the cow's milk.

Structure

The F17G adhesin is a two-domain adhesin (TDA) located at the F17 fimbrial tip. The determination of the crystal structure of the F17G lectin domain led to the discovery of the variable immunoglobulin-like structure as a paradigm for bacterial fimbrial TDAs [1]. F17G has a shallow groove for carbohydrate recognition on its flank.


File:F17G_Igfold.jpg

Biological roles of GBP-ligand interaction

The F17G fimbrial lectin enhances intestinal colonization in the early life of ruminants. The long and flexible F17 fimbriae can penetrate deep between intestinal microvilli, where the fimbrial tip adhesin finds its glycan receptors. The subsequent secretion of heat stable and heat lable toxins can lead to severe diarhea.

CFG resources used in investigations

The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the CFG database search results for fimbriae and pili.

Glycan profiling


Glycogene microarray


Knockout mouse lines


Glycan array

F17G adhesins have been screened for their glycan specificity (click here). To see all glycan array results for F17G adhesin, click here.

Related GBPs

FedF, CfaE, FimH, PapG, CupB6

The specificity of some of the other fimbrial tip adhesins was determined by CFG glycan array analysis (P. gingivalis fimbriae, E. coli FedF adhesin, E. coli CfaE adhesin from CFA/I pili)

References

  1. 1.0 1.1 Buts, L., Bouckaert, J., De Gents, E., Loris, R., Oscarson, S., Lahmann, M., Messens, J., Brosens, E., Wyns, L. & De Greve, H. (2003). The fimbrial adhesin F17-G of enterotoxigenic Escherichia coli has an immunoglobulin-like lectin domain that binds N-acetylglucosamine. Mol. Microb. 49, 705-715.
  2. Merckel, M. C., Tanskanen, J., Edelman, S., Westerlund-Wilkström, B., Korhonen, T. K. & Goldman, A. (2003). The structural basis of receptor-binding by Escherichia coli associaed with diarrhea and septicemia. J. Mol. Biol. 331, 897-905.
  3. Coddens, A., Diswall, M., Angstrom, J., Breimer, M. E., Goddeeris, B., Cox, E. & Teneberg, S. (2009). Recognition of blood group ABH type 1 determinants by the FedF adhesin of F18-fimbriated Escherichia coli. J Biol Chem 284, 9713-26.
  4. Poole, S. T., McVeigh, A. L., Anantha, R. P., Lee, L. H., Akay, Y. M., Pontzer, E. A., Scott, D. A., Bullitt, E. & Savarino, S. J. (2007). Donor strand complementation governs intersubunit interaction of fimbriae of the alternate chaperone pathway. Mol Microbiol 63, 1372-84.
  5. Bouckaert, J., Berglund, J., Schembri, M., De Gents, E., Cools, L., Wuhrer, M., Hung, C.-S., Pinkner, J., Slättegard, R., Savialov, A., Choudhury, D., Langermann, S., Hultgren, S. J., Wyns, L., Klemm, P., Oscarson, S., Knight, S. D. & De Greve, H. (2005). Receptor binding studies disclose a novel class of high-affinity inhibitors of the Escherichia coli FimH adhesin. Mol. Microb. 55, 441-455.
  6. Dodson, K. W., Pinkner, J. S., Rose, T., Magnusson, G., Hultgren, S. J. & Waksman, G. (2001). Structural basis of the interaction of the pyelonephritic E. coli adhesin to ist human kideny receptor. Cell 105, 733-743.
  7. De Greve, H., Wyns, L. & Bouckaert, J. (2007). Combining sites of bacterial fimbriae. Curr Opin Struct Biol 17, 506-12.
  8. Sauer, F. G., Barnhart, M., Choudhury, D., Knight, S. D., Waksman, G. & Hultgren, S. J. (2000). Chaperone-assisted pilus assembly and bacterial attachment. Curr Opin Struct Biol 10, 548-56.
  9. De Kerpel, M., Van Molle, I., Brys, L., Wyns, L., De Greve, H. & Bouckaert, J. (2006). N-terminal truncation enables crystallization of the receptor-binding domain of the FedF bacterial adhesin. Acta Crystallogr Sect F Struct Biol Cryst Commun 62, 1278-82.
  10. Mouricout, M., Milhavet, M., Durié, C., Grange, P. Characterization of glycoprotein glycan receptors for Escherichia coli F17 fimbrial lectin, Microb. Pathog. (1995) 18, 297-306
  11. Lipman, L.J.A., de Nijs A., Gaastra W.. Isolation and identification of fimbriae and toxin production by Escherichia coli strains from cows with clinical mastitis, Vet. Microbiology 47 (1995) p. 1-7

Acknowledgements

The CFG is grateful to the following PIs for their contributions to this wiki page: Alisdair Boraston, Julie Bouckaert, Anne Imberty

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