Stabilization of bound polycyclic aromatic hydrocarbons by a π-cation interaction
Résumé
Proteins can use aromatic side-chains to stabilize bound cationic ligands through cation-p interactions. Here, we report the ®rst example of the reciprocal process, termed p-cation, in which a cationic protein side-chain stabilizes a neutral aromatic ligand. Site-directed mutagenesis revealed that an arginine side-chain located in the deep binding pocket of a monoclonal antibody (4D5) is essential for binding the neutral polynuclear aromatic hydrocarbon benzo[a]pyrene. This Arg was very likely selected for in the primary response, further underscoring the importance of the p-cation interaction for ligand binding, which should be considered in protein analysis and design when ligands include aromatic groups.