Oligomeric rings of the Sec61p complex induced by ligands required for protein translocation.
The heterotrimeric Sec61p complex is a major component of the protein-conducting channel of the endoplasmic reticulum (ER) membrane, associating with either ribosomes or the Sec62/63 complex to perform co- and posttranslational transport, respectively. We show by electron microscopy that purified mammalian and yeast Sec61p complexes in detergent form cylindrical oligomers with a diameter of approximately 85 A and a central pore of approximately 20 A. Each oligomer contains 3-4 heterotrimers. Similar ring structures are seen in reconstituted proteoliposomes and native membranes. Oligomer formation by the reconstituted Sec61p complex is stimulated by its association with ribosomes or the Sec62/63p complex. We propose that these cylindrical oligomers represent protein-conducting channels of the ER, formed by ligands specific for co- and posttranslational transport.
Hanein
D
D
Department of Biophysics, Boston University School of Medicine, Massachusetts 02218-2394, USA.
Matlack
K E
KE
Jungnickel
B
B
Plath
K
K
Kalies
K U
KU
Miller
K R
KR
Rapoport
T A
TA
Akey
C W
CW
D000818:Animals; D001692:Biological Transport; D002451:Cell Compartmentation; D003902:Detergents; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000648:ultrastructure*; D005614:Freeze Fracturing; D005656:Fungal Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins; D007089:Image Enhancement; D015640:Ion Channel Gating; D007473:Ion Channels / Q000648:ultrastructure*; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism / Q000648:ultrastructure*; D026901:Membrane Transport Proteins; D008954:Models, Biological; D008970:Molecular Weight; D009038:Motion; D016624:Negative Staining; D010316:Particle Size; D011485:Protein Binding; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011510:Proteolipids / Q000648:ultrastructure*; D012270:Ribosomes / Q000378:metabolism; D000069816:SEC Translocation Channels; D029701:Saccharomyces cerevisiae Proteins; D015003:Yeasts
D003902:Detergents; D005656:Fungal Proteins; D006360:Heat-Shock Proteins; D007473:Ion Channels; D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011510:Proteolipids; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; C074213:SEC62 protein, S cerevisiae; C074215:SEC63 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C020485:proteoliposomes