Biochemical and Structural Characterization of the Novel Sialic Acid-Binding Site of Escherichia Coli Heat-Labile Enterotoxin Lt-Iib.Zalem, D., Ribeiro, J.P., Varrot, A., Lebens, M., Imberty, A., Teneberg, S.
(2016) Biochem.J. 473: 3923
- PubMed: 27562297
- DOI: 10.1042/BCJ20160575
- PubMed Abstract:
The structurally related AB <sub>5 </sub>-type heat-labile enterotoxins of Escherichia coli and Vibrio cholerae are classified into two major types. The type I group includes cholera toxin (CT) and E. coli LT-I, whereas the type II subfamily comprise ...
The structurally related AB 5 -type heat-labile enterotoxins of Escherichia coli and Vibrio cholerae are classified into two major types. The type I group includes cholera toxin (CT) and E. coli LT-I, whereas the type II subfamily comprises LT-IIa, LT-IIb and LT-IIc. The carbohydrate-binding specificities of LT-IIa, LT-IIb and LT-IIc are distinctive from those of cholera toxin and E. coli LT-I. Whereas CT and LT-I bind primarily to the GM1 ganglioside, LT-IIa binds to gangliosides GD1a, GD1b and GM1, LT-IIb binds to the GD1a and GT1b gangliosides, and LT-IIc binds to GM1, GM2, GM3 and GD1a. These previous studies of the binding properties of type II B-subunits have been focused on ganglio core chain gangliosides. To further define the carbohydrate binding specificity of LT-IIb B-subunits, we have investigated its binding to a collection of gangliosides and non-acid glycosphingolipids with different core chains. A high-affinity binding of LT-IIb B-subunits to gangliosides with a neolacto core chain, such as Neu5Gcα3- and Neu5Acα3-neolactohexaosylceramide, and Neu5Gcα3- and Neu5Acα3-neolactooctaosylceramide was detected. An LT-IIb-binding ganglioside was isolated from human small intestine and characterized as Neu5Acα3-neolactohexaosylceramide. The crystal structure of the B-subunit of LT-IIb with the pentasaccharide moiety of Neu5Acα3-neolactotetraosylceramide (Neu5Ac-nLT: Neu5Acα3Galβ4GlcNAcβ3Galβ4Glc) was determined providing the first information for a sialic-binding site in this subfamily, with clear differences from that of CT and LT-I.
Institute of Biomedicine, Department of Medical Biochemistry and Cell Biology, The Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.,Centre de Recherches sur les Macromolécules Végétales (UPR5301, CNRS and University Grenoble Alpes), BP53, F-38041 Grenoble Cedex 09, France.,Institute of Biomedicine, Department of Medical Microbiology and Immunology, The Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.