Molecular modeling of human MT2 melatonin receptor: the role of Val204, Leu272 and Tyr298 in ligand binding

Abstract

A model of the helical part of the human MT2 melatonin (hMT2) receptor, a member of the G protein-coupled receptors superfamily has been generated, based on the structure of bovine rhodopsin. Modeling has been combined with sitedirected mutagenesis to investigate the role of the specific amino acid residues within the transmembrane domains (TM) numbers V, VI and VII of hMT2 receptor in the interaction with 2-iodomelatonin. Saturation binding assays with 2-iodomelatonin demonstrated that the substitution V204A (TMV) resulted in total loss of binding while the mutation V205A had no effect. The replacement of F209 with alanine led to a significant decrease in the Bmax value of receptor binding while mutations V205A and F209A also within TM V did not significantly change binding properties of the hMT2 receptor. In the case of TM VI, the substitution G271T caused substantial decrease in 2-iodomelatonin binding to the hMT2 receptor. The change L272A (TM VI) as well as mutation Y298A within TM VII completely abolished ligand binding to the receptor. These data suggest that several new amino acid residues within TM V, VI and VII are involved in ligand-MT2 receptor interaction.

Computer aided comparative analysis of the binding modes of the adenosine receptor agonists for all known subtypes of adenosine receptors

“…The second point which has to be noted is that the available structure of rhodopsin was obtained for its ground state, which is probably not the best starting point for a molecular modeling study of the binding modes of adenosine receptor agonists. On the other hand, several examples of the successful use of rhodopsin-based models of GPCRs in studies of agonist binding modes have been published [59][60][61]. Since in the present study we are considering the static agonist binding mode (not the process of the receptor activation), and taking into account a great amount of experimental data of sitedirected mutagenesis of the adenosine receptors we presume it to be acceptable to use the structure of rhodopsin as a template for model construction.…”

Melatonin Receptor Agonists: SAR and Applications to the Treatment of Sleep-Wake Disorders

“…While the crystal structure of the 2 -adrenergic receptor has been recently resolved [112][113][114], traditional GPCR models had been based on the crystal structure of bacteriorhodopsin or bovine rhodopsin. In fact, several models of MT 1 and MT 2 receptors were described, built by homology modeling from bacteriorhodopsin [73,115] or rhodopsin [84,[116][117][118][119][120] structure and employing the amino acid sequence of Xenopus or human receptors. These models propose different docking solutions and interaction schemes for MLT and other agonists, and they are partially consistent with available mutagenesis data.…”

International Union of Basic and Clinical Pharmacology. LXXV. Nomenclature, Classification, and Pharmacology of G Protein-Coupled Melatonin Receptors

“…MELATONIN RECEPTORS ligand binding. Mazna et al (2004) identified several amino acids in TM V (Val204), VI (Leu272), and VII (Tyr298) that are involved in melatonin interactions with the MT 2 melatonin receptor binding pocket. In a subsequent studies, this group demonstrated that residues Asn268 and Ala275 in TM6 as well as residues Val291 and Leu295 in TM7 are essential for 2-iodomelatonin binding to the hMT 2 receptor (Mazna et al, 2005).…”