SEC61B Human

The Sec61 translocon is a proteinaceous channel composed of three subunits: α, β, and γ. The α subunit forms the actual channel through which nascent polypeptide chains enter the ER. The β (SEC61B) and γ subunits are associated with the channel on the periphery and are in contact with the lipid bilayer .

SEC61B is not essential in yeast but is commonly used as a marker of the ER. In higher eukaryotes, such as Drosophila, deletion of SEC61B causes lethality, indicating its critical physiological role . SEC61B interacts directly with microtubules, and its depletion induces ER stress in both mammalian cells and Caenorhabditis elegans .

The translocation of proteins across the ER membrane is the first step in the biogenesis of secretory and membrane proteins. Proteins enter the ER via the Sec61 translocon. If the mature protein does not possess specific signals for retention in the ER, it exits the ER and is transported to the Golgi complex. From the Golgi, the protein is either transported to endocytic organelles or to the plasma membrane .

Mutations or dysregulation of SEC61B have been associated with various diseases, including polycystic liver disease and other liver-related conditions . The precise mechanisms by which SEC61B contributes to these diseases are still under investigation.

Recombinant SEC61B is used in various research applications to study its role in protein translocation and ER homeostasis. Overexpression of SEC61B containing small epitope tags induces dramatic bundling of the ER and microtubules, providing insights into the physiological function of ER-microtubule interaction .