title: Interaction of the cotranslational Hsp70 Ssb with ribosomal proteins and rRNA depends on its lid domain.
abstract: Cotranslational chaperones assist in de novo folding of nascent polypeptides in all organisms. In yeast, the heterodimeric ribosome-associated complex (RAC) forms a unique chaperone triad with the Hsp70 homologue Ssb. We report the X-ray structure of full length Ssb in the ATP-bound open conformation at 2.6 Å resolution and identify a positively charged region in the α-helical lid domain (SBDα), which is present in all members of the Ssb-subfamily of Hsp70s. Mutational analysis demonstrates that this region is strictly required for ribosome binding. Crosslinking shows that Ssb binds close to the tunnel exit via contacts with both, ribosomal proteins and rRNA, and that specific contacts can be correlated with switching between the open (ATP-bound) and closed (ADP-bound) conformation. Taken together, our data reveal how Ssb dynamics on the ribosome allows for the efficient interaction with nascent chains upon RAC-mediated activation of ATP hydrolysis.
authors.affiliation: Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Gumiero
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.|BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Conz
authors.affiliation: Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany.
authors.forename: Genís Valentín
authors.initials: GV
authors.lastname: Gesé
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.|BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany.
authors.forename: Felix Alexander
authors.initials: FA
authors.lastname: Weyer
authors.affiliation: Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany.
authors.forename: Karine
authors.initials: K
authors.lastname: Lapouge
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Kappes
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: von Plehwe
authors.affiliation: Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany.
authors.forename: Géza
authors.initials: G
authors.lastname: Schermann
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.|BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Edith
authors.initials: E
authors.lastname: Fitzke
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.|BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Wölfle
authors.affiliation: Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany.
authors.forename: Tamás
authors.initials: T
authors.lastname: Fischer
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.|BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Rospert
authors.affiliation: Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany.
authors.forename: Irmgard
authors.initials: I
authors.lastname: Sinning
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D018360:Crystallography, X-Ray; D019204:GTP-Binding Proteins / Q000378:metabolism* / Q000648:ultrastructure; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism* / Q000648:ultrastructure; D010445:Peptide Elongation Factors / Q000378:metabolism* / Q000648:ultrastructure; D000072756:Protein Conformation, alpha-Helical; D012335:RNA, Ribosomal / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: C077247:HBS1 protein, S cerevisiae; D018840:HSP70 Heat-Shock Proteins; D010445:Peptide Elongation Factors; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D019204:GTP-Binding Proteins