Schematic illustration of ER-ligand binding dynamics using biosensors and operational mechanisms. (A) Depicts a FRET-based biosensor designed to visualize ligand engagement through conformational transitions in the ER alpha (ERα) ligand-binding domain (LBD), resulting in fluorescence resonance energy transfer (FRET) that detects these interactions (54). (B) Presents a fluorescence complementation-based biosensor that exposes conformational changes in the ERα LBD upon ligand engagement, enabling visualization through the activation of mVenus fluorescence (55). (C) Details a time-resolved FRET (TR-FRET)-based assay employing fluorescent dyes to verify the interaction between ERα LBD and coactivators following ligand engagement (57). (D) Describes a FRET-based biosensor that utilizes fluorescent proteins to confirm interactions between the ERα LBD and coactivators post-ligand binding (56). (E) Illustrates a BRET-based membrane-target biosensor that employs bioluminescence resonance energy transfer to authenticate conformational modifications in the ERα LBD triggered by ligand binding, with membrane localization enabled by a membrane localization sequence (MLS) (59). europium (Eu), streptavidin (SA), biotin (B), mNeptune (mNep), and membrane localization sequence (MLS) are denoted.
