title: The signal recognition particle binds to protein L23 at the peptide exit of the Escherichia coli ribosome.
abstract: The signal recognition particle (SRP) from Escherichia coli, composed of Ffh protein and 4.5S RNA, mediates membrane targeting of translating ribosomes displaying a signal or signal-anchor sequence. SRP binds at the peptide exit of the large ribosomal subunit. Structural details of the interaction are not known. Here, the position of Ffh or SRP on the ribosome was probed by using site-specific UV-induced crosslinking by p-azidophenacyl bromide (AzP) attached to a number of cysteine residues engineered into surface positions of Ffh. Efficient crosslinking to vacant ribosomes took place from two positions (AzP17 and AzP25) in the N domain of Ffh, both with Ffh and SRP. Both AzP17 and AzP25 were predominantly crosslinked to ribosomal protein L23 that is located at the peptide exit of the 50S subunit. The SRP receptor, FtsY, did not change the crosslink pattern, whereas the presence of a nascent signal peptide on the ribosome resulted in a second crosslink between Ffh(AzP17) and protein L23, indicating that binding to the nascent signal peptide induced a slightly different arrangement of SRP on the ribosome. These results indicate a model of the topographical arrangement of SRP at the peptide exit of the 50S ribosomal subunit.
authors.affiliation: Institute of Molecular Biology, University of Witten/Herdecke, 58448 Witten, Germany.
authors.forename: Shan-Qing
authors.initials: SQ
authors.lastname: Gu
authors.forename: Frank
authors.initials: F
authors.lastname: Peske
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Wieden
authors.forename: Marina V
authors.initials: MV
authors.lastname: Rodnina
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wintermeyer
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D003432:Cross-Linking Reagents; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D012329:RNA, Bacterial; D012335:RNA, Ribosomal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D018271:Signal Recognition Particle / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: C409968:4.5S RNA; D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; C087406:FtsY protein, Bacteria; D012329:RNA, Bacterial; D012335:RNA, Ribosomal; D018160:Receptors, Cytoplasmic and Nuclear; D012269:Ribosomal Proteins; D018271:Signal Recognition Particle; C043816:ribosomal protein L23, E coli