title: The bacterial translocon SecYEG opens upon ribosome binding.
abstract: In co-translational translocation, the ribosome funnel and the channel of the protein translocation complex SecYEG are aligned. For the nascent chain to enter the channel immediately after synthesis, a yet unidentified signal triggers displacement of the SecYEG sealing plug from the pore. Here, we show that ribosome binding to the resting SecYEG channel triggers this conformational transition. The purified and reconstituted SecYEG channel opens to form a large ion-conducting channel, which has the conductivity of the plug deletion mutant. The number of ion-conducting channels inserted into the planar bilayer per fusion event roughly equals the number of SecYEG channels counted by fluorescence correlation spectroscopy in a single proteoliposome. Thus, the open probability of the channel must be close to unity. To prevent the otherwise lethal proton leak, a closed post-translational conformation of the SecYEG complex bound to a ribosome must exist.
authors: Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria.
authors: Denis G
authors: DG
authors: Knyazev
authors: Alexander
authors: A
authors: Lents
authors: Eberhard
authors: E
authors: Krause
authors: Nicole
authors: N
authors: Ollinger
authors: Christine
authors: C
authors: Siligan
authors: Daniel
authors: D
authors: Papinski
authors: Lukas
authors: L
authors: Winter
authors: Andreas
authors: A
authors: Horner
authors: Peter
authors: P
authors: Pohl
mesh_terms: D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015640:Ion Channel Gating; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism; D008051:Lipid Bilayers / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding; D021381:Protein Transport; D012270:Ribosomes / Q000378:metabolism*; D000069816:SEC Translocation Channels; D013050:Spectrometry, Fluorescence
chemical_list: D029968:Escherichia coli Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; D008563:Membrane Lipids; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli; C088616:SecG protein, E coli; C057841:SecY protein, E coli
keywords: Channel Gating; Membrane Bilayer; Membrane Biophysics; Membrane Reconstitution; Permeability; Protein Translocation
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