title: The methionine-rich domain of the 54 kDa subunit of signal recognition particle is sufficient for the interaction with signal sequences.
abstract: The signal recognition particle (SRP) binds to signal sequences when they emerge from a translating ribosome and targets the complex of ribosome, nascent chain and SRP to the membrane of the rough endoplasmic reticulum (rER) allowing the co-translational translocation of the nascent chain. By photo-crosslinking it has been shown that the signal sequence of preprolactin (PPL) only interacts with the methionine-rich (M) domain of the 54 kDa protein subunit (SRP54) of SRP. Here we show that (i) a signal-anchor sequence is likewise crosslinked only to the methionine-rich domain of SRP54, (ii) free SRP54 can interact with signal sequences independently of the other components of SRP, (iii) its M domain suffices to perform this function, and (iv) an essentially intact M domain is required for signal sequence recognition. Alkylation of the N+G domain in intact SRP54 with N-ethyl maleimide (NEM), but not after cleavage with V8 protease, prevents the binding of a signal sequence to the M domain. This suggests a proximity between the N+G and M domains of SRP54 and raises the possibility that the role of the N+G domain may be to regulate the binding and/or the release of signal sequences.
authors.affiliation: Cell Biology Programme, European Molecular Biology Laboratory, Heidelberg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Lütcke
authors.forename: S
authors.initials: S
authors.lastname: High
authors.forename: K
authors.initials: K
authors.lastname: Römisch
authors.forename: A J
authors.initials: AJ
authors.lastname: Ashford
authors.forename: B
authors.initials: B
authors.lastname: Dobberstein
mesh_terms: D000818:Animals; D001389:Azirines / Q000494:pharmacology*; D001565:Benzoates; D001665:Binding Sites; D002474:Cell-Free System; D002872:Chromosome Deletion; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D008239:Lysine; D046911:Macromolecular Substances; D008715:Methionine; D008970:Molecular Weight; D011388:Prolactin / Q000235:genetics* / Q000378:metabolism; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D021382:Protein Sorting Signals / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D018271:Signal Recognition Particle; D014158:Transcription, Genetic
chemical_list: D001389:Azirines; D001565:Benzoates; D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D011498:Protein Precursors; D021382:Protein Sorting Signals; D012261:Ribonucleoproteins; D018271:Signal Recognition Particle; C017671:preprolactin; C051320:4-(3-trifluoromethyldiazirino)benzoic acid; D011388:Prolactin; D003513:Cycloheximide; D008715:Methionine; D008239:Lysine