title: Ribosome binding induces repositioning of the signal recognition particle receptor on the translocon.
abstract: Cotranslational protein targeting delivers proteins to the bacterial cytoplasmic membrane or to the eukaryotic endoplasmic reticulum membrane. The signal recognition particle (SRP) binds to signal sequences emerging from the ribosomal tunnel and targets the ribosome-nascent-chain complex (RNC) to the SRP receptor, termed FtsY in bacteria. FtsY interacts with the fifth cytosolic loop of SecY in the SecYEG translocon, but the functional role of the interaction is unclear. By using photo-cross-linking and fluorescence resonance energy transfer measurements, we show that FtsY-SecY complex formation is guanosine triphosphate independent but requires a phospholipid environment. Binding of an SRP-RNC complex exposing a hydrophobic transmembrane segment induces a rearrangement of the SecY-FtsY complex, which allows the subsequent contact between SecY and ribosomal protein uL23. These results suggest that direct RNC transfer to the translocon is guided by the interaction between SRP and translocon-bound FtsY in a quaternary targeting complex.
authors.affiliation: Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Faculty of Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Kuhn
authors.affiliation: Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
authors.forename: Albena
authors.initials: A
authors.lastname: Draycheva
authors.affiliation: Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Faculty of Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Vogt
authors.affiliation: Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Faculty of Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany.
authors.forename: Narcis-Adrian
authors.initials: NA
authors.lastname: Petriman
authors.affiliation: Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany.
authors.forename: Lukas
authors.initials: L
authors.lastname: Sturm
authors.affiliation: Department of Biochemistry and Functional Proteomics, Faculty of Biology and BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany.
authors.forename: Friedel
authors.initials: F
authors.lastname: Drepper
authors.affiliation: Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Department of Biochemistry and Functional Proteomics, Faculty of Biology and BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Warscheid
authors.affiliation: Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wintermeyer
authors.affiliation: Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Hans-Georg.Koch@biochemie.uni-freiburg.de.
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Koch
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry; D001667:Binding, Competitive; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry; D026901:Membrane Transport Proteins / Q000737:chemistry; D011485:Protein Binding; D014176:Protein Biosynthesis; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry; D018000:Receptors, Peptide; D012270:Ribosomes / Q000737:chemistry; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D018271:Signal Recognition Particle
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C087406:FtsY protein, Bacteria; D008055:Lipids; D026901:Membrane Transport Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D000069816:SEC Translocation Channels; C057841:SecY protein, E coli; D018271:Signal Recognition Particle; C036318:signal peptide receptor; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins