Cryo-EM Structures Reveal Nonmirror-Image Binding of L- and D-Peptide Enantiomers at α7 Nicotinic Acetylcholine Receptor.

Peptides targeting the α7 nicotinic acetylcholine receptor (α7-nAChR) hold significant potential for biological research and therapeutic applications. Notably, linear D-amino acid peptides exhibit higher inhibitory potency against α7-nAChR and greater proteolytic stability compared to their L-type counterparts, making them more attractive candidates for both laboratory research and clinical use. However, the molecular basis of D-peptide binding to α7-nAChR remains elusive. Herein, cryo-EM structures of α7-nAChR is presented in complex with the L-peptide ^LKP1794 (2.68 Å) and its D-peptide enantiomer ^DKP1794 (2.53 Å), providing the first molecular insights into D-peptide recognition by α7-nAChR. Structural analysis reveals that both peptides occupy the orthosteric site of α7-nAChR. However, their binding poses are not merely mirror images; instead, they adopt a hybrid binding mode that combines mirror symmetry with a flipped peptide backbone orientation. Our structural data uncover a distinct D-peptide binding mechanism that diverges from the hypothesized retro-inversion model.