title: The bacterial SRP receptor, FtsY, is activated on binding to the translocon.
abstract: Proteins are inserted into the bacterial plasma membrane cotranslationally after translating ribosomes are targeted to the translocon in the membrane via the signal recognition particle (SRP) pathway. The targeting pathway involves an interaction between SRP and the SRP receptor, FtsY. Here we focus on the role of FtsY and its interaction with the translocon in controlling targeting. We show that in unbound FtsY the NG and A domains interact with one another. The interaction involves the membrane-targeting region at the junction between A and N domain. The closed form of FtsY is impaired in binding to SRP. Upon binding to the phospholipid-embedded translocon the domains of FtsY move apart. This enhances the docking of the FtsY NG domain to the homologous NG domain of the SRP protein Ffh. Thus, FtsY binding to the translocon has a central role in orchestrating the formation of a quaternary transfer complex in which the nascent peptide is transferred to the translocon. We propose that FtsY activation at the translocon ensures that ribosome-SRP complexes are directed to available translocons. This way sequestering SRP in futile complexes with unbound FtsY can be avoided and efficient targeting to the translocon achieved.
authors.affiliation: Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Albena
authors.initials: A
authors.lastname: Draycheva
authors.affiliation: Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bornemann
authors.affiliation: Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Sergey
authors.initials: S
authors.lastname: Ryazanov
authors.affiliation: Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany. nils-alexander.lakomek@phys.chem.ethz.ch.|Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, Solid-state NMR, ETH Zürich, Zürich, Switzerland. nils-alexander.lakomek@phys.chem.ethz.ch.
authors.forename: Nils-Alexander
authors.initials: NA
authors.lastname: Lakomek
authors.affiliation: Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany. wolfgang.wintermeyer@mpibpc.mpg.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wintermeyer
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D000072417:Protein Domains; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018271:Signal Recognition Particle / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C087406:FtsY protein, Bacteria; D018160:Receptors, Cytoplasmic and Nuclear; D018271:Signal Recognition Particle