title: The mammalian and yeast translocon complexes comprise a characteristic Sec61 channel.
abstract: In eukaryotes, protein translocation across and insertion into the membrane of the endoplasmic reticulum (ER) is facilitated by a protein-conducting channel, the Sec61 complex or translocon. In our previous electrophysiological studies, we characterized the mammalian Sec61 channel from Canis familiaris. Here we extended these initial results to the Sec61 channel from the yeast Saccharomyces cerevisiae and compared the basic electrophysiological properties of both channel preparations with respect to the gating behaviour, distribution of channel open states, ionic conductance, approximated pore dimensions, reversal potential and selectivity as well as voltage-dependent open probability. We found that the Sec61 complexes from both species displayed conformable characteristics of the highly dynamic channel in an intrinsically open state. In contrast, the bacterial Sec61-homologue, the SecYEG complex from Escherichia coli, displayed under the same experimental conditions significantly different properties residing in an intrinsically closed state. We therefore propose that considerable differences between the respective eukaryote and prokaryote protein-conducting channel units and their regulation exist.
authors.affiliation: Biophysik, Universität Osnabrück, FB Biologie/Chemie, 49076 Osnabrück, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Erdmann
authors.forename: Martin
authors.initials: M
authors.lastname: Jung
authors.forename: Patrick
authors.initials: P
authors.lastname: Maurer
authors.forename: Anke
authors.initials: A
authors.lastname: Harsman
authors.forename: Richard
authors.initials: R
authors.lastname: Zimmermann
authors.forename: Richard
authors.initials: R
authors.lastname: Wagner
mesh_terms: D000818:Animals; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D011487:Protein Conformation; D021381:Protein Transport; D000069816:SEC Translocation Channels; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000069816:SEC Translocation Channels; C490684:SEC6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C102455:Sec61 gamma protein, Canis familiaris; D033921:Vesicular Transport Proteins