Component of a ribosome-associated endoplasmic reticulum (ER) translocon complex involved in multi-pass membrane protein transport into the ER membrane and biogenesis (PubMed:32820719). Together with SEC61 and TMCO1, forms the lipid-filled cavity at the center of the translocon where TMEM147 may insert hydrophobic segments of mutli-pass membrane proteins from the lumen into de central membrane cavity in a process gated by SEC61, and TMCO1 may insert hydrophobic segments of nascent chains from the cytosol into the cavity (PubMed:32820719). Acts as a negative regulator of CHRM3 function, most likely by interfering with its trafficking to the cell membrane. Negatively regulates CHRM3-mediated calcium mobilization and activation of RPS6KA1/p90RSK activity (PubMed:21056967). Forms a complex with NCLN/Nicalin and NOMO, resulting in a stabilization of the 3 proteins, which are otherwise quickly degraded by the proteasome (PubMed:20538592). Interacts with CHRM3, CHRM1 and AVPR2 (PubMed:21056967). 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).