title: The crystal structure of the signal recognition particle Alu RNA binding heterodimer, SRP9/14.
abstract: The mammalian signal recognition particle (SRP) is an 11S cytoplasmic ribonucleoprotein that plays an essential role in protein sorting. SRP recognizes the signal sequence of the nascent polypeptide chain emerging from the ribosome, and targets the ribosome-nascent chain-SRP complex to the rough endoplasmic reticulum. The SRP consists of six polypeptides (SRP9, SRP14, SRP19, SRP54, SRP68 and SRP72) and a single 300 nucleotide RNA molecule. SRP9 and SRP14 proteins form a heterodimer that binds to the Alu domain of SRP RNA which is responsible for translation arrest. We report the first crystal structure of a mammalian SRP protein, that of the mouse SRP9/14 heterodimer, determined at 2.5 A resolution. SRP9 and SRP14 are found to be structurally homologous, containing the same alpha-beta-beta-beta-alpha fold. This we designate the Alu binding module (Alu bm), an additional member of the family of small alpha/beta RNA binding domains. The heterodimer has pseudo 2-fold symmetry and is saddle like, comprising a strongly curved six-stranded amphipathic beta-sheet with the four helices packed on the convex side and the exposed concave surface being lined with positively charged residues.
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation, France.
authors.forename: D E
authors.initials: DE
authors.lastname: Birse
authors.forename: U
authors.initials: U
authors.lastname: Kapp
authors.forename: K
authors.initials: K
authors.lastname: Strub
authors.forename: S
authors.initials: S
authors.lastname: Cusack
authors.forename: A
authors.initials: A
authors.lastname: Aberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid; D018271:Signal Recognition Particle / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C490326:SRP14 protein, human; C486350:SRP9 protein, human; D018271:Signal Recognition Particle; C490325:Srp14 protein, mouse; C503637:Srp72 protein, mouse; C107410:Srp9 protein, mouse; D012313:RNA