6ial | pdb_00006ial
Porcine E.coli heat-labile enterotoxin B-pentamer in complex with Lacto-N-neohexaose
Structural highlights
FunctionELBP_ECOLX The biological activity of the toxin is produced by the A chain, which activates intracellular adenyl cyclase. Publication Abstract from PubMedDiarrhea 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 A crystal structure of pLTB in complex with branched lacto-N-neohexaose (Galbeta4GlcNAcbeta6[Galbeta4GlcNAcbeta3]Galbeta4Glc). 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. Specificity of Escherichia coli Heat-Labile Enterotoxin Investigated by Single-Site Mutagenesis and Crystallography.,Heggelund JE, Heim JB, Bajc G, Hodnik V, Anderluh G, Krengel U Int J Mol Sci. 2019 Feb 6;20(3). pii: ijms20030703. doi: 10.3390/ijms20030703. PMID:30736336[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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