A–C, GABA docked into GABA receptor models of RDL (A), GABA_A (B), and GABA_C (C) receptors, which have cation-π interaction with different residues in the binding site (loop B Tyr, loop A Tyr, and loops B and C Tyrs, respectively). D, Example of multiple aromatic residues contributing to a cation-π interaction in the enzyme gai 1 (Gallivan and Dougherty, 2000).