SEC61 Beta (SEC61b)

SEC61B is a subunit of the heteromeric SEC61 complex, which also contains alpha (SEC61A1) and gamma (SEC61G) subunits. The SEC61 complex forms the core of the mammalian endoplasmic reticulum (ER) translocon, a transmembrane channel for the translocation of proteins across the ER membrane.The Sec61 subunits are also observed in the post-ER compartment, suggesting that these proteins can escape the ER and recycle back. CFTR could be coimmunoprecipitated in a complex with SEC61B in the cytosolic fraction of HeLa cells, suggesting that CFTR can be cut from the membrane in complex with SEC61B. SEC61B escorts complex membrane proteins through the SEC61 complex in the retrograde direction for degradation by the proteasome or other proteolytic systems.