Multivalent Calixarene Complexation of a Designed Pentameric Lectin

We describe complex formation between a designed pentameric beta-propeller and the anionic macrocycle sulfonato-calix[8]arene (sclx(8)), as characterized by X-ray crystallography and NMR spectroscopy. Two crystal structures and N-15 HSQC experiments reveal a single calixarene binding site in the concave pocket of the beta-propeller toroid. Despite the symmetry mismatch between the pentameric protein and the octameric macrocycle, they form a high affinity multivalent complex, with the largest protein-calixarene interface observed to date. This system provides a platform for investigating multivalency.