Within the recent crystallographic X-ray structure of the CXCR4 chemokine receptor bound into a cyclic peptide antagonist, a specific interaction between position 6. 58 and the peptide was discovered. Therefore, place 6. 58 may possibly serve as a typical position for the binding of both proteins and small molecule ligands. Finally, in our research position 2. 61, which will be occupied with a Glutamic acid in hPKRs, was found to be essential for antagonist binding, because an electrostatic interaction might be established between the positive charge on the ligand and this negatively-charged residue. This could explain the need for the positive charge about the identified small molecule antagonists, which was indeed deduced from the structure activity analysis. The ligands positive charge might communicate with the negatively-charged residue in receptor place 2. 61, which was also proved to be important in ligand binding within the dopamine receptors. To sum up, the observed relationships reinforce the expected putative binding site and might support the principle that family A GPCRs share a standard little molecule binding pocket inside the TM cavity, regardless of the type of their cognate ligand. Docking of ligands to a single experimental or model structure of a GPCR receptor is demonstrated to reproduce the binding mode of the ligands in several cases, to enrich identified ligands in structure based virtual screening campaigns, and to rationalize specificity profiles of GPCR antagonists and thus was the approach taken here. In many non GPCR circumstances, good docking have now been described using multiple receptor conformations. This kind of method was effective for a sequence identity array of 30?60% between available templates and models. Although GPCR homology models routinely have a lower sequence identity to their potential layouts, using sets of multiple homology models or of a perturbed X-ray framework may none the less be a sensible method, as was recently described. Recent innovations in X-ray structure determination of GPCRs may permit systematic screening of the best receptor structure representation and of docking performance, contrary to the benchmark of experimental structures. Identification of potential novel hPKR binders Our research employed SAR of known hPKR binders to recognize novel potential binders of hPKR1, and highlighted possible off-target effects of FDA approved drugs. Interestingly, the story individuals share little architectural chemical similarity with the recognized hPKR binders but share the exact same pharmacophores and similar putative interactions within the TM deal binding site. This kind of scaffold moving effect is common and is often sought after in drug development. The term is based on the assumption that the same desired biological activity might be achieved by various molecules that maintain a number of the essential chemical features as the template molecule, i. Elizabeth.