Recent advances on structure and dynamics of G protein–coupled receptors using single-molecule Förster resonance energy transfer

G protein-coupled receptors (GPCRs) mediate cellular responses to a wide array of extracellular stimuli, including photons, ions, small molecules, peptides, and proteins, orchestrating nearly all physiological processes. This superfamily is divided into classes A (rhodopsin), B (secretin and adhesion), C (glutamate), and F (frizzled/taste2) based on homology and phylogenetic studies. Once perceived as simple on/off switches, GPCRs are now recognized for their dynamic nature, transitioning between multiple states. As such, their study continues to challenge classical structural biology approaches. In this context, we highlight recent advances in single-molecule Förster resonance energy transfer (smFRET) as a tool to complement structural and biophysical methods to probe GPCR structure and dynamics. We discuss the key advantages and limitations of smFRET, review recent technological adaptations and advancements, and address the ongoing challenges in achieving a comprehensive understanding of GPCR dynamics.