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). Component of the Golgi to ER traffic (GET) complex, which is composed of GET1/WRB, CAMLG/GET2 and GET3/TRC40 (PubMed:21444755, PubMed:23041287, PubMed:24392163, PubMed:32910895). Within the complex, GET1 and CAMLG form a heterotetramer which is stabilized by phosphatidylinositol binding and which binds to the GET3 homodimer (PubMed:32910895). Interacts with CAMLG (via C-terminus) (PubMed:23041287, PubMed:31417168, PubMed:32187542). GET3 shows a higher affinity for CAMLG than for GET1 (PubMed:24392163). Belongs to the WRB/GET1 family.