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

Autor: Julie Elisabeth Heggelund, Joel Benjamin Heim, Gregor Bajc, Vesna Hodnik, Gregor Anderluh, Ute Krengel
Jazyk: angličtina
Rok vydání: 2019
Předmět:
Zdroj: International Journal of Molecular Sciences, Vol 20, Iss 3, p 703 (2019)
Druh dokumentu: article
ISSN: 1422-0067
20030703
DOI: 10.3390/ijms20030703
Popis: 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.
Databáze: Directory of Open Access Journals
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