N-Terminal protein complexation and assembly with a triangular sulfated macrocycle

We report two cocrystal structures of a mutant Ralstonia solanacearum lectin (RSL) in complex with the recently described sulfated terphen[3]arene (STP3). This triangular macrocycle bearing 12 sulfates exhibits interesting protein-binding modes including methionine encapsulation and insertion between surface-exposed loops. These two binding modes facilitate the overall crystal packing, which may benefit from the macrocycle rigidity. In addition to a promising tool for protein assembly and crystallization, the data have implications for lectin–heparan sulfate interactions.