Understanding the Selectivity of Genistein for Human Estrogen Receptor-β Using X-Ray Crystallography and Computational Methods

AbstractWe present X-ray crystallographic and molecular modeling studies of estrogen receptors-α and -β complexed with the estrogen receptor-β-selective phytoestrogen genistein, and coactivator-derived NR box peptides containing an LXXLL motif. We demonstrate that the ligand binding mode is essentially identical when genistein is bound to both isoforms, despite the considerably weaker affinity of this ligand for estrogen receptor-α. In addition, we examine subtle differences between binding site residues, providing an explanation for why genistein is modestly selective for the β isoform. To this end, we also present the results of quantum chemical studies and thermodynamic arguments that yield insight to the nature of the interactions leading to estrogen receptor-β selectivity. The importance of our analysis to structure-based drug design is discussed

An inverse agonist of orphan receptor GPR61 acts by a G protein-competitive allosteric mechanism

Abstract GPR61 is an orphan GPCR related to biogenic amine receptors. Its association with phenotypes relating to appetite makes it of interest as a druggable target to treat disorders of metabolism and body weight, such as obesity and cachexia. To date, the lack of structural information or a known biological ligand or tool compound has hindered comprehensive efforts to study GPR61 structure and function. Here, we report a structural characterization of GPR61, in both its active-like complex with heterotrimeric G protein and in its inactive state. Moreover, we report the discovery of a potent and selective small-molecule inverse agonist against GPR61 and structural elucidation of its allosteric binding site and mode of action. These findings offer mechanistic insights into an orphan GPCR while providing both a structural framework and tool compound to support further studies of GPR61 function and modulation