Component of a ribosome-associated translocon complex involved in multi-pass membrane protein transport into the endoplasmic reticulum (ER) membrane and biogenesis (PubMed:32820719). May antagonize Nodal signaling and subsequent organization of axial structures during mesodermal patterning, via its interaction with NOMO (By similarity). Forms a complex with NOMO and TMEM147, resulting in a stabilization of the 3 proteins, which are otherwise quickly degraded by the proteasome (PubMed:20538592). The ribosome-associated ER translocon complex includes SEC61A1, SEC61B, SEC61G, TMCO1, CCDC47, NCLN/Nicalin, NOMO and TMEM147; in the absence of ribosomes, only the complex forms with NCLN/Nicalin, NOMO and TMEM147 remains intact (PubMed:32820719). Participates in a large protein complex, which is not related to the gamma-secretase complex (PubMed:15257293). Highly expressed in pancreas and skeletal muscle and, at lower levels, in heart. Belongs to the nicastrin family. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.