Novel binding site identified in a hybrid between cholera toxin and heat-labile enterotoxin: 1.9 A crystal structure reveals the details

Asa Holmner; Michael Lebens; Susann Teneberg; Jonas Angström; Mats Okvist; Ute Krengel

doi:10.1016/j.str.2004.06.022

Novel binding site identified in a hybrid between cholera toxin and heat-labile enterotoxin: 1.9 A crystal structure reveals the details

Structure. 2004 Sep;12(9):1655-67. doi: 10.1016/j.str.2004.06.022.

Authors

Asa Holmner¹, Michael Lebens, Susann Teneberg, Jonas Angström, Mats Okvist, Ute Krengel

Affiliation

¹ Department of Chemistry and Bioscience, Chalmers University of Technology, PO Box 462, SE-40530 Göteborg, Sweden. asa.holmner@chembio.chalmers.se

PMID: 15341730
DOI: 10.1016/j.str.2004.06.022

Abstract

A hybrid between the B subunits of cholera toxin and Escherichia coli heat-labile enterotoxin has been described, which exhibits a novel binding specificity to blood group A and B type 2 determinants. In the present investigation, we have determined the crystal structure of this protein hybrid, termed LCTBK, in complex with the blood group A pentasaccharide GalNAcalpha3(Fucalpha2)Galbeta4(Fucalpha3)GlcNAcbeta, confirming not only the novel binding specificity but also a distinct new oligosaccharide binding site. Binding studies revealed that the new specificity can be ascribed to a single mutation (S4N) introduced into the sequence of Escherichia coli heat-labile enterotoxin. At a resolution of 1.9 A, the new binding site is resolved in excellent detail. Main features include a complex network of water molecules, which is well preserved by the parent toxins, and an unexpectedly modest contribution to binding by the critical residue Asn4, which interacts with the ligand only via a single water molecule.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Asparagine / metabolism
Bacterial Toxins / chemistry*
Bacterial Toxins / genetics
Bacterial Toxins / metabolism
Binding Sites
Blood Group Antigens / metabolism
Cholera Toxin / chemistry*
Cholera Toxin / genetics
Cholera Toxin / metabolism
Crystallography, X-Ray
Drug Design
Enterotoxins / chemistry*
Enterotoxins / genetics
Enterotoxins / metabolism
Escherichia coli Proteins / chemistry*
Escherichia coli Proteins / genetics
Escherichia coli Proteins / metabolism
Glycosphingolipids / chemistry
Glycosphingolipids / metabolism
Humans
Models, Molecular
Molecular Sequence Data
Molecular Structure
Oligosaccharides / chemistry
Oligosaccharides / metabolism
Protein Binding
Protein Structure, Tertiary*
Protein Subunits / chemistry*
Protein Subunits / genetics
Protein Subunits / metabolism
Recombinant Fusion Proteins / chemistry*
Recombinant Fusion Proteins / genetics
Recombinant Fusion Proteins / metabolism
Water / chemistry

Substances

Bacterial Toxins
Blood Group Antigens
Enterotoxins
Escherichia coli Proteins
Glycosphingolipids
Oligosaccharides
Protein Subunits
Recombinant Fusion Proteins
Water
Asparagine
Cholera Toxin
heat-labile enterotoxin, E coli

Associated data

PDB/1TL0