Required for the post-translational delivery of tail-anchored (TA) proteins to the endoplasmic reticulum (ER) (PubMed:21444755, PubMed:23041287, PubMed:24392163, PubMed:27226539). Together with CAMLG/GET2, acts as a membrane receptor for soluble GET3/TRC40, which recognizes and selectively binds the transmembrane domain of TA proteins in the cytosol (PubMed:21444755, PubMed:23041287, PubMed:24392163, PubMed:27226539). Required to ensure correct topology and ER insertion of CAMLG (PubMed:31417168, PubMed:32187542).