Guanine nucleotide exchange factor for Gpa1p; amplifies G-protein signaling; subunit of the GET complex involved in ATP-dependent Golgi-to-ER trafficking; binds as a dimer to the transmembrane domain of tail-anchored proteins in the cytosol, shielding them from aqueous solvent until the Get1p/Get2p heterodimer releases the substrate and inserts it into the ER membrane; acts as a chaperone under ATP-depleted oxidative stress conditions; protein abundance increases under DNA replication stress