Abstract 2468 A comprehensive analysis of predicted protein structures identifies a new human GPCR family

Similar protein sequences encode similar folds.However, recent advances in sequence-to-structure predictions enable us to find exceptions to this rule.Here, we use millions of AlphaFold2 (AF2) predictions to identify two families of "superdark" seven-transmembrane proteins (7TMPs) in humans that resemble but lack sequence similarity to known G protein-coupled receptors (GPCRs).We show that these superdark families have some GPCR-like characteristics, including b-arrestin recruitment and G protein receptor kinase (GRK) phosphorylation.Furthermore, we show that one superdark, SD1, recruits and regulates mTOR signaling.Unlike most GPCRs, SD1 resides in intracellular vesicles that rapidly traverse the cytoskeleton via microtubules.Lastly, we show that SD1 has archaeal origins and fully rescues the vacuolar defects caused by deleting its yeast homolog.Together, these findings mark significant breakthroughs in illuminating dark proteins and mTOR signaling biology.