A hypothesis concerning the translocation of nascent polypeptides across the endoplasmic reticulum membrane. As shown in the diagram below, soon after the signal sequence peptide of the nascent chain emerges from the ribosome it is recognized by a specific receptor called the signal recognition particle (SRP). The second component of the translocation process is the docking protein. It is bound to the surface of the ER membrane, and it serves as a receptor for the SRP. Since the SRP binds to both the docking protein and the signal sequence of the protein being translated, it serves to bring the ribosome into the vicinity of the ER membrane. Subsequently, the ribosome binds to a ribosome receptor on the ER and the nascent polypeptide is threaded through a pore in the membrane and into the ER lumen. A peptidase then removes the signal peptide from the newly synthesized protein molecule. See Chronology, 1975, Blobel and Dobberstein; 1991, Simon and Blobel; leader sequence peptide, signal hypothesis, signal recognition particle, translation, translocon.
The mRNA is moving from left to right in this diagram.
Subjects: Genetics and Genomics.