Propoxazepam conformation and its orientation in the GABAA-receptor binding site

V. B. Larionov, M. Ya. Golovenko, A. S. Reder


Introduction. One of 1.4-benzodiazepine 3-alcoxy derivatives – propoxazepam, possessing high analgetic action, also effectively suppressed different experimental seizures types. Unexpected combination of pharmacological spectrum components suggests its different binding sites of GABAA receptor.
The aim of the work was to determine the geometry of the ligand-receptor complexes of GABA-RC using experimental data of the propoxazepam conformation and calculated data for the three-dimensional structure of the ligandbinding site and subsequent docking to characterize its binding to this receptor.
Materials and methods. X-ray diffraction studies of the compound were performed using Xcalibur 3 single crystal X-ray diffractometer. Calculation of the molecular docking parameters was performed using the iGEMDOCK v2.1 program for the GABA receptor (GABA (A) R-beta3 homopentamer, 4COF), the molecular structures of propoxazepam conformers were prepared using ChemAxon (MarvinSketch 17.11.0).
Results and discussion. Based on the X-ray diffraction analysis, the coordinates of the atoms, bond lengths and valence angles in the propoxazepam molecule were calculated, it is found that it form crystallographic twins as racemate. The molecular docking method showed that propoxazepam several binding sites with the energy of complex formation from -78.64 to -85.29 kcal/mol exist on the isolated site of the GABA-receptor.
Conclusions. The highest contribution to the formation of the bond of the complex is carried out by residues of polar amino acids (serine, asparagine, methionine and arginine in polar binding sub-center). However, also for individual conformers, aromatic amino acids, predominantly phenylalanine (Phe-31, Ala-135 – hydrophobic binding sub-center) make a significant contribution.


propoxazepam; X-ray diffraction; docking; GABAA-recepto

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