title: A structural step into the SRP cycle.
abstract: Co-translational targeting of secretory and membrane proteins to the translocation machinery is mediated by the signal recognition particle (SRP) and its membrane-bound receptor (SR) in all three domains of life. Although the overall composition of the SRP system differs, the central ribonucleoprotein core and the general mechanism of GTP-dependent targeting are highly conserved. Recently, structural studies have contributed significantly to our understanding of the molecular organization of SRP. SRP appears as a structurally flexible particle modulated and regulated by its interactions with the ribosome-nascent chain complex, the translocon and the SR. The SRP core (SRP54 with its cognate RNA binding site) plays a central role in these interactions and communicates the different binding states by long-range interdomain communication. Based on recent structures of SRP54, a model for signal peptide binding stimulating the GTP affinity during the first step of the SRP cycle is presented. The model is placed in the context of the recent structures of mammalian SRP bound to a ribosome-nascent chain complex and of a subcomplex of SRP-SR.
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg (BZH), Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany. Klemens.Wild@bzh.uni-heidelberg.de
authors.forename: Klemens
authors.initials: K
authors.lastname: Wild
authors.forename: Ken R
authors.initials: KR
authors.lastname: Rosendal
authors.forename: Irmgard
authors.initials: I
authors.lastname: Sinning
mesh_terms: D006160:Guanosine Triphosphate / Q000378:metabolism; D046911:Macromolecular Substances; D008958:Models, Molecular; D011485:Protein Binding; D014176:Protein Biosynthesis; D021382:Protein Sorting Signals / Q000502:physiology; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000502:physiology*; D018000:Receptors, Peptide / Q000737:chemistry* / Q000502:physiology*; D012270:Ribosomes / Q000502:physiology; D018271:Signal Recognition Particle / Q000737:chemistry* / Q000502:physiology*
chemical_list: D046911:Macromolecular Substances; D021382:Protein Sorting Signals; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D018271:Signal Recognition Particle; C036318:signal peptide receptor; D006160:Guanosine Triphosphate