Required for the post-translational delivery of tail-anchored (TA) proteins to the endoplasmic reticulum. Together with GET2, acts as a membrane receptor for soluble GET3, which recognizes and selectively binds the transmembrane domain of TA proteins in the cytosol. The GET complex cooperates with the HDEL receptor ERD2 to mediate the ATP-dependent retrieval of resident ER proteins that contain a C-terminal H-D-E-L retention signal from the Golgi to the ER