Component of a ribosome-associated translocon complex involved in multi-pass membrane protein transport into the endoplasmic reticulum (ER) membrane and biogenesis (By similarity). 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. 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. Participates in a large protein complex, which is not related to the gamma-secretase complex. Belongs to the nicastrin family.