title: Posttranslational protein transport in yeast reconstituted with a purified complex of Sec proteins and Kar2p.
abstract: We have reproduced the posttranslational mode of protein translocation across the endoplasmic reticulum membrane with reconstituted proteoliposomes containing a purified complex of seven yeast proteins. This Sec complex includes a heterotrimeric Sec61p complex, homologous to that in mammals, as well as all other membrane proteins found in genetic screens for translocation components. Efficient posttranslational translocation also requires the addition of lumenal Kar2p (BiP) and ATP. The trimeric Sec61p complex also exists as a separate entity that, in contrast with the large Sec complex, is associated with membrane-bound ribosomes. We therefore hypothesize that distinct membrane protein complexes function in co- and posttranslational translocation pathways.
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, Berlin-Buch, Federal Republic of Germany.
authors.forename: S
authors.initials: S
authors.lastname: Panzner
authors.forename: L
authors.initials: L
authors.lastname: Dreier
authors.forename: E
authors.initials: E
authors.lastname: Hartmann
authors.forename: S
authors.initials: S
authors.lastname: Kostka
authors.forename: T A
authors.initials: TA
authors.lastname: Rapoport
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001692:Biological Transport; D005656:Fungal Proteins / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D012270:Ribosomes / Q000378:metabolism; D000069816:SEC Translocation Channels; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment
chemical_list: D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; C060153:KAR2 protein, yeast; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000255:Adenosine Triphosphate