title: Protein transport by purified yeast Sec complex and Kar2p without membranes.
abstract: Posttranslational protein translocation across the endoplasmic reticulum membrane of yeast requires a seven-component transmembrane complex (the Sec complex) in collaboration with the lumenal Kar2 protein (Kar2p). A translocation substrate was initially bound to the cytosolic face of the purified Sec complex in a signal-sequence-dependent but Kar2p- and nucleotide-independent manner. In a subsequent reaction, in which Kar2p interacted with the lumenal face of the Sec complex and hydrolyzed adenosine triphosphate, the substrate moved through a channel formed by the Sec complex and was released at the lumenal end. Movement through the channel occurred in detergent solution in the absence of a lipid bilayer.
authors.affiliation: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Matlack
authors.forename: K
authors.initials: K
authors.lastname: Plath
authors.forename: B
authors.initials: B
authors.lastname: Misselwitz
authors.forename: T A
authors.initials: TA
authors.lastname: Rapoport
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport; D003432:Cross-Linking Reagents; D003600:Cytosol / Q000378:metabolism; D003902:Detergents; D004072:Digitonin; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins; D008051:Lipid Bilayers; D008081:Liposomes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D011498:Protein Precursors / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000378:metabolism; D011510:Proteolipids / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D000069816:SEC Translocation Channels; D029701:Saccharomyces cerevisiae Proteins; D012995:Solubility; D013388:Succinimides
chemical_list: D003432:Cross-Linking Reagents; D003902:Detergents; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C060153:KAR2 protein, yeast; D008051:Lipid Bilayers; D008081:Liposomes; C048632:MF(ALPHA)1 protein, S cerevisiae; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; D011510:Proteolipids; D000069816:SEC Translocation Channels; C074213:SEC62 protein, S cerevisiae; C074215:SEC63 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013388:Succinimides; C020485:proteoliposomes; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D004072:Digitonin; C019358:disuccinimidyl suberate