Translocon

The translocon (also called a translocator or translocation channel) is a general term for a protein channel in biological membranes that functions to move polypeptides across the membrane or insert them into the lipid bilayer. This structure is a key component of the protein translocation pathway in all organisms, from bacteria, archaea, and eukaryotes.

In eukaryotes the term translocon most commonly refers to the complex that transports nascent polypeptides with a targeting signal sequence from the cytosol into the interior (cisternal or lumenal) space of the endoplasmic reticulum (ER). This translocation process requires the protein to cross a hydrophobic lipid bilayer. The same complex is also used to integrate nascent proteins into the membrane itself (membrane proteins). In prokaryotes, a similar protein complex transports polypeptides across the (inner) plasma membrane or integrates membrane proteins. In either case, the protein complex is formed from Sec proteins (Sec: secretory), with the hetero-trimeric Sec61 being the channel. In prokaryotes, the homologous channel complex is known as SecYEG.