A posttargeting signal sequence recognition event in the endoplasmic reticulum membrane.
We have analyzed early phases of the cotranslational transport of the secretory protein preprolactin through the mammalian endoplasmic reticulum (ER) membrane. Following recognition of the signal sequence of the nascent polypeptide chain in the cytosol by the SRP, the chain is transferred into the membrane, where a second signal sequence recognition step takes place for which the presence in the lipid bilayer of the Sec61p complex is essential and sufficient. This step leads to a tight junction between the ribosomenascent chain complex and the Sec61p complex, and to the productive insertion of the nascent chain into the translocation site. These results show that a translocation substrate is subjected to two recognition events before being allowed to cross the ER membrane.
Jungnickel
B
B
Max Delbrück Center for Molecular Medicine, Berlin-Buch, Federal Republic of Germany.
Rapoport
T A
TA
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D008051:Lipid Bilayers; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011388:Prolactin / Q000096:biosynthesis* / Q000378:metabolism*; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D000069816:SEC Translocation Channels; D014158:Transcription, Genetic
D008051:Lipid Bilayers; D008565:Membrane Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; D011510:Proteolipids; D012333:RNA, Messenger; D011994:Recombinant Proteins; D000069816:SEC Translocation Channels; C020485:proteoliposomes; C017671:preprolactin; D011388:Prolactin