Mechanisms of transmembrane protein integration Transmembrane proteins, which are partly integrated into the ER membrane rather than released into the ER lumen, have a complex assembly process. The initial stages are similar to soluble proteins: a signal sequence starts the insertion into the ER membrane. However, this process is interrupted by a stop-transfer sequence—a string of hydrophobic amino acids—which causes the translocator to halt and release the protein laterally into the membrane. This results in a single-pass transmembrane protein with one end inside the ER lumen and the other in the cytosol, and this orientation is permanent.
Mechanisms of transmembrane protein integration Transmembrane proteins which are partly integrated into the ER membrane rather than released into the ER lumen have a complex assembly process The initial stages are similar to soluble proteins a signal sequence starts the insertion into the ER membrane However this process is interrupted by a stop-transfer sequence—a string of hydrophobic amino acids—which causes the translocator to halt and release the protein laterally into the membrane This results in a single-pass transmembrane protein with one end inside the ER lumen and the other in the cytosol and this orientation is permanent