title: The influence of ligand valency on aggregation mechanisms for inhibiting bacterial toxins.
abstract: Divalent and tetravalent analogues of ganglioside GM1 are potent inhibitors of cholera toxin and Escherichia coli heat-labile toxin. However, they show little increase in inherent affinity when compared to the corresponding monovalent carbohydrate ligand. Analytical ultracentrifugation and dynamic light scattering have been used to demonstrate that the multivalent inhibitors induce protein aggregation and the formation of space-filling networks. This aggregation process appears to arise when using ligands that do not match the valency of the protein receptor. While it is generally accepted that multivalency is an effective strategy for increasing the activity of inhibitors, here we show that the valency of the inhibitor also has a dramatic effect on the kinetics of aggregation and the stability of intermediate protein complexes. Structural studies employing atomic force microscopy have revealed that a divalent inhibitor induces head-to-head dimerization of the protein toxin en route to higher aggregates.
authors.affiliation: School of Chemistry, University of Leeds, UK.
authors.forename: Cristina
authors.initials: C
authors.lastname: Sisu
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Baron
authors.forename: Hilbert M
authors.initials: HM
authors.lastname: Branderhorst
authors.forename: Simon D
authors.initials: SD
authors.lastname: Connell
authors.forename: Carel A G M
authors.initials: CA
authors.lastname: Weijers
authors.forename: Renko
authors.initials: R
authors.lastname: de Vries
authors.forename: Edward D
authors.initials: ED
authors.lastname: Hayes
authors.forename: Aliaksei V
authors.initials: AV
authors.lastname: Pukin
authors.forename: Michel
authors.initials: M
authors.lastname: Gilbert
authors.forename: Roland J
authors.initials: RJ
authors.lastname: Pieters
authors.forename: Han
authors.initials: H
authors.lastname: Zuilhof
authors.forename: Gerben M
authors.initials: GM
authors.lastname: Visser
authors.forename: W Bruce
authors.initials: WB
authors.lastname: Turnbull
mesh_terms: D001427:Bacterial Toxins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D004768:Enterotoxins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D011485:Protein Binding / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D020836:Protein Structure, Quaternary; D013816:Thermodynamics
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D008024:Ligands; D005677:G(M1) Ganglioside; C027538:heat-labile enterotoxin, E coli