The Sec61 translocon is a heterotrimeric complex comprising alpha, beta and gamma subunits localized to the membrane of the endoplasmic reticulum. Nascent polypeptides bound to the signal recognition particle (SRP) first interact with the SRP receptor and are then transferred to the Sec61 translocon, which either integrates the protein into the lipid bilayer or translocates it across the membrane to enter the secretory pathway. (Adapted from PMID:23414305.)