Molecular modelling of UH-301 and 5-HT1a receptor interactions

A three-dimensional model of the human 5-HT1a receptor was constructed by molecular modelling, and the molecular and electronic structures of (R)- and (S)-5-fluoro-8-hydroxy-2-(dipropylamino)tetralin (UH-301) and of (R)- and (S)-8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT) were examined by molecular mechanics and quantum mechanics calculations and molecular dynamics simulations, The receptor model has seven transmembrane alpha-helices (TMHs), organized according to a projection map of visual rhodopsin, and includes all loops between helices and the N- and C-terminal parts, Interactions of UH-301 and 8-OH-DPAT with the 5-HT1a receptor were examined by molecular dynamics simulations and energy minimization of receptor-ligand complexes. 8-OH-DPAT had lower electrostatic potentials around the hydroxyl group and stronger hydrogen bonding to the receptor model than had UH-301. The simulations indicated that the 5-HT1a receptor agonists, (R)- and (S)-8-OH-DPAT and (R)-UH-301, interacted with the receptor at a site closer to Asp82 in TMH2 than did (S)-UH-301, which is a 5-HT1a receptor antagonist, Simulations of receptor-ligand complexes indicated that Asp82, Asp116, Ser199, Thr200 and Ile385 are essential for binding of both agonist and antagonist to the receptor.