In silico analysis of Human and Zebrafish ?-2 Adrenergic Receptors

Abstract

?-2 adrenoceptors, belong to class of  Rhodopsin-like G-protein coupled receptors. Proteins of the G-protein coupled receptor (GPCR) family are involved in many pathophysiological conditions and hence are targets for various drug discovery methods. The current information on the structure of GPCRs is limited to few structures like Rhodopsin, ? adrenergic receptors, adenosine A2A receptors, Human Dopamine D3 and Chemokine receptor. In our study ?-2 adrenergic receptors of Human and Zebrafish were modeled using MODELLER with Human Dopamine D3 receptor (PDB ID: 3PBL) as template.  Through our modeling studies we have identified the critical role played by Proline residues (2.38, 2.59, 4.39, 4.59, 4.60, 7.50) of transmembrane helices and extracellular loop in stabilizing structural deviations in the transmembrane. Novel ligand binding residues S/T (6.56) and F (7.35) along with the positional significance of Y (3.28), Y (6.55) in regulating function were identified. Our models have shown that the Phenylalanine at 7.39 in TM7 can favourably interact with positively charged N-methyl group of the catecholamine ligands via hydrophobic contacts rather than 7.38 as reported previously. Furthermore, we are able to correctly show the orientation of Serine at 5.42 and 5.46 and discuss the relevance of residues at position 3.37 and 5.43 in the receptor regulation. We also demonstrate and propose that the orientation of V (2.61)/S should be taken into account in drug/ pharmacophore design specific for ?-2 adrenergic receptors. We believe that these findings will open new lead for ligand/ pharmacophore design, in silico leading further to experimental validation using Zebrafish as experimental model.

Keywords: ?-2 adrenergic receptor, Zebrafish, ligand binding, residue conservation, homology modeling, ionic lock, toggle switch.