The pharmacologic properties of gold compounds have been known since the end of the 19th century. In the last decade, gold complexes have received increased attention due to the variety of their applications. Rhodopsin-like receptors are a family of proteins that belong to the largest group of G protein-coupled receptors (GPCRs).
In this paper, the molecular interactions between active binding sites of the Rhodopsin-like receptor (RLR) and synthesized gold(III) complex ([Au(DPP)Cl2]+ where DPP=4,7-diphenyl-1,10-phenanthroline) were investigated by molecular docking simulations. The crystal structure of investigated receptor RLR (PDB ID: 4A4M) was extracted from RCSB Protein Data Bank in PDB format. The native bound ligand (11-cis-retinal) was extracted from the receptor and binding pocket analysis was performed. Re-docking was performed with the gold(III) complex to generate the same docking pose as found in the co-crystallized form of the receptor.
The binding energy of the gold(III) complex to RLR was found to be -35.35 kJ/mol, as opposed to 11-cis-retinal which of about -40.5 kJ/mol. The obtained results revealed that gold(III) complex binds at the same binding pockets to RLR, as well as a native bound ligand, by weak non-covalent interactions. The most prominent interactions are hydrogen bonds, alkyl-π, and π-π interactions. The preliminary results suggest that the gold(III) complex showed good binding affinity against RLR, as well as a native bound ligand, 11-cis-retinal, as evident from the free binding energy (ΔGbind in kJ/mol).
