Using single-molecule FRET to study the dynamics of GPCR - G protein ternary complexes

Larissa Oriana Silva¹

Alyssa Gonneville²

Gabriella Sprague¹ 

Daniel Alec Nutter¹

Rajan Lamichhane² 

Matthew T. Eddy¹

1) University of Florida
2) University of Tennessee, Knoxville

G protein-coupled receptors (GPCRs) play a significant role in human physiology, making them promising drug targets. They initiate cellular signaling events through interactions with their intracellular partner G protein upon binding of external stimuli, such as hormones, neurotransmitters, and small molecule drugs. Determining the lifetime of the GPCR – G protein ternary complexes among differing conditions, such as ligand efficacy or lipid environment, is essential to understanding how these proteins signal and thus will allow for an enhancement in current therapeutic designs. Here, we leverage single-molecule FRET (smFRET) to study how differing ligand efficacies impact the lifetime of the A_2A adenosine receptor (A_2AAR) and mini-G_s, a G protein variant engineered to facilitate structural studies. We find that the two proteins complex under both agonist bound and antagonist bound conditions, but the behavior of this complex differs depending on the ligand efficacy.