The protein-conducting channel in the membrane of the endoplasmic reticulum is open laterally toward the lipid bilayer.
Lipids and proteins were found to contact a nascent type II membrane protein, as well as a nascent secretory protein, during their insertion into the membrane of the endoplasmic reticulum. This suggests that the protein-conducting channel is open laterally toward the lipid bilayer during an early stage of protein insertion. Contact to lipids was confined to the hydrophobic core region of the respective signal or signal anchor sequence. Thus, the nascent polypeptide is positioned in the translocation complex such that the signal or signal anchor sequence faces the lipid bilayer, whereas the hydrophilic, translocating portion is in proteinaceous environment.
Martoglio
B
B
Zentrum für Molekulare Biologie, Universität Heidelberg, Federal Republic of Germany.
Hofmann
M W
MW
Brunner
J
J
Dobberstein
B
B
D000944:Antigens, Differentiation, B-Lymphocyte; D001692:Biological Transport; D016764:Cell Polarity; D003432:Cross-Linking Reagents; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure*; D000949:Histocompatibility Antigens Class II / Q000378:metabolism* / Q000648:ultrastructure; D008051:Lipid Bilayers; D008562:Membrane Glycoproteins / Q000378:metabolism* / Q000648:ultrastructure; D008566:Membranes / Q000648:ultrastructure; D008954:Models, Biological; D010743:Phospholipids / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000378:metabolism; D018271:Signal Recognition Particle / Q000378:metabolism
D000944:Antigens, Differentiation, B-Lymphocyte; D003432:Cross-Linking Reagents; D000949:Histocompatibility Antigens Class II; D008051:Lipid Bilayers; D008562:Membrane Glycoproteins; D010743:Phospholipids; D011498:Protein Precursors; D021382:Protein Sorting Signals; D018271:Signal Recognition Particle; C045084:invariant chain; C017671:preprolactin; D011388:Prolactin