Specificity of Escherichia coli Heat-Labile Enterotoxin Investigated by Single-Site Mutagenesis and Crystallography

Heggelund, Julie Elisabeth; Heim, Joel Benjamin; Bajc, Gregor; Hodnik, Vesna; Anderluh, Gregor; Krengel, Ute

doi:10.3390/ijms20030703

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Specificity of Escherichia coli Heat-Labile Enterotoxin Investigated by Single-Site Mutagenesis and Crystallography

Julie Elisabeth Heggelund

^1,†,

¹,

²,

^2,3,‡,

and

^1,*

Department of Chemistry, University of Oslo, Postbox 1033 Blindern, 0315 Oslo, Norway

Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia

Department of Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana; Slovenia

Author to whom correspondence should be addressed.

^†

Current address: Department of Pharmacy, University of Oslo, Postbox 1068 Blindern, 0316 Oslo, Norway.

^‡

Current address: Lek d.d., Kolodvorska 27, 1234 Mengeš, Slovenia.

Int. J. Mol. Sci. 2019, 20(3), 703; https://doi.org/10.3390/ijms20030703

Received: 28 January 2019 / Accepted: 31 January 2019 / Published: 6 February 2019

(This article belongs to the Special Issue Protein–Carbohydrate Interactions: Structure–Function Relationships)

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Abstract

Diarrhea caused by enterotoxigenic Escherichia coli (ETEC) is one of the leading causes of mortality in children under five years of age and is a great burden on developing countries. The major virulence factor of the bacterium is the heat-labile enterotoxin (LT), a close homologue of the cholera toxin. The toxins bind to carbohydrate receptors in the gastrointestinal tract, leading to toxin uptake and, ultimately, to severe diarrhea. Previously, LT from human- and porcine-infecting ETEC (hLT and pLT, respectively) were shown to have different carbohydrate-binding specificities, in particular with respect to N-acetyllactosamine-terminating glycosphingolipids. Here, we probed 11 single-residue variants of the heat-labile enterotoxin with surface plasmon resonance spectroscopy and compared the data to the parent toxins. In addition we present a 1.45 Å crystal structure of pLTB in complex with branched lacto-N-neohexaose (Galβ4GlcNAcβ6[Galβ4GlcNAcβ3]Galβ4Glc). The largest difference in binding specificity is caused by mutation of residue 94, which links the primary and secondary binding sites of the toxins. Residue 95 (and to a smaller extent also residues 7 and 18) also contribute, whereas residue 4 shows no effect on monovalent binding of the ligand and may rather be important for multivalent binding and avidity. View Full-Text

Keywords: bacterial toxin; cholera toxin; Escherichia coli heat-labile enterotoxin; lectin; N-acetyllactosamine binding; neutral glycosphingolipids; protein–carbohydrate interactions; surface plasmon resonance spectroscopy; X-ray crystal structure

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MDPI and ACS Style

Heggelund, J.E.; Heim, J.B.; Bajc, G.; Hodnik, V.; Anderluh, G.; Krengel, U. Specificity of Escherichia coli Heat-Labile Enterotoxin Investigated by Single-Site Mutagenesis and Crystallography. Int. J. Mol. Sci. 2019, 20, 703. https://doi.org/10.3390/ijms20030703

AMA Style

Heggelund JE, Heim JB, Bajc G, Hodnik V, Anderluh G, Krengel U. Specificity of Escherichia coli Heat-Labile Enterotoxin Investigated by Single-Site Mutagenesis and Crystallography. International Journal of Molecular Sciences. 2019; 20(3):703. https://doi.org/10.3390/ijms20030703

Chicago/Turabian Style

Heggelund, Julie E., Joel B. Heim, Gregor Bajc, Vesna Hodnik, Gregor Anderluh, and Ute Krengel. 2019. "Specificity of Escherichia coli Heat-Labile Enterotoxin Investigated by Single-Site Mutagenesis and Crystallography" International Journal of Molecular Sciences 20, no. 3: 703. https://doi.org/10.3390/ijms20030703

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Specificity of Escherichia coli Heat-Labile Enterotoxin Investigated by Single-Site Mutagenesis and Crystallography

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