Figure 1.

Strategy for re-engineering the CTB protein to prepare a pentavalent neoglycoprotein inhibitor for cholera toxin. The N termini of a nonbinding CTB mutant W88E are oxidized to give aldehydes that undergo oxime ligation with a carbohydrate ligand that bears an aminooxy function. The resulting neoglycoprotein has ligand groups arranged with optimal spacing to bind to the cholera toxin protein. In the 3D structure of CTB (PDB code: 3CHB),[24] the binding sites are marked in white, and N-terminal threonine residues are marked with black arrows.