title: Solution and crystallographic studies of branched multivalent ligands that inhibit the receptor-binding of cholera toxin.
abstract: The structure-based design of multivalent ligands offers an attractive strategy toward high affinity protein inhibitors. The spatial arrangement of the receptor-binding sites of cholera toxin, the causative agent of the severe diarrheal disease cholera and a member of the AB(5) bacterial toxin family, provides the opportunity of designing branched multivalent ligands with 5-fold symmetry. Our modular synthesis enabled the construction of a family of complex ligands with five flexible arms each ending with a bivalent ligand. The largest of these ligands has a molecular weight of 10.6 kDa. These ligands are capable of simultaneously binding to two toxin B pentamer molecules with high affinity, thus blocking the receptor-binding process of cholera toxin. A more than million-fold improvement over the monovalent ligand in inhibitory power was achieved with the best branched decavalent ligand. This is better than the improvement observed earlier for the corresponding nonbranched pentavalent ligand. Dynamic light scattering studies demonstrate the formation of concentration-dependent unique 1:1 and 1:2 ligand/toxin complexes in solution with no sign of nonspecific aggregation. This is in complete agreement with a crystal structure of the branched multivalent ligand/toxin B pentamer complex solved at 1.45 A resolution that shows the specific 1:2 ligand/toxin complex formation in the solid state. These results reiterate the power of the structure-based design of multivalent protein ligands as a general strategy for achieving high affinity and potent inhibition.
authors.affiliation: Biomolecular Structure Center and Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Zhongsheng
authors.initials: Z
authors.lastname: Zhang
authors.forename: Ethan A
authors.initials: EA
authors.lastname: Merritt
authors.forename: Misol
authors.initials: M
authors.lastname: Ahn
authors.forename: Claudia
authors.initials: C
authors.lastname: Roach
authors.forename: Zheng
authors.initials: Z
authors.lastname: Hou
authors.forename: Christophe L M J
authors.initials: CL
authors.lastname: Verlinde
authors.forename: Wim G J
authors.initials: WG
authors.lastname: Hol
authors.forename: Erkang
authors.initials: E
authors.lastname: Fan
mesh_terms: D001665:Binding Sites; D002772:Cholera Toxin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018360:Crystallography, X-Ray; D005677:G(M1) Ganglioside / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005690:Galactose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D008024:Ligands; D008027:Light; D008958:Models, Molecular; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012542:Scattering, Radiation; D012996:Solutions
chemical_list: D008024:Ligands; D011956:Receptors, Cell Surface; D012996:Solutions; C023552:choleragen receptor; D005677:G(M1) Ganglioside; D002772:Cholera Toxin; D005690:Galactose