In the ER, protein translocation across the membrane occurs via the embedded protein complex called the translocon. It encompasses a core protein-conducting Sec61 complex and other accessory protein complexes that associate with Sec61 constantly or temporarily when required. The Sec61 complex has a main vertical channel secured by a short α helix that acts as a plug and opens and closes as required. It allows hydrophilic protein segments to translocate into the ER lumen. Sec61 also has a lateral gate that opens like a clamshell to transfer hydrophobic domains of transmembrane proteins into the ER membrane. Close to the Sec61 channel, integral membrane proteins, Sec62 and Sec63 form a subcomplex. They assist in the post-translational translocation of some secretory proteins. The oligosaccharyltransferase complex is also an integral translocon component that adds complex sugar molecules to specific residues of a polypeptide to form a glycoprotein. Other complexes like the signal peptidase transiently associate with the Sec61 channel to cleave the signal peptide from the polypeptide chain.