title: Multivalent contacts of the Hsp70 Ssb contribute to its architecture on ribosomes and nascent chain interaction.
abstract: Hsp70 chaperones assist de novo folding of newly synthesized proteins in all cells. In yeast, the specialized Hsp70 Ssb directly binds to ribosomes. The structural basis and functional mode of recruitment of Ssb to ribosomes is not understood. Here, we present the molecular details underlying ribosome binding of Ssb in Saccharomyces cerevisiae. This interaction is multifaceted, involving the co-chaperone RAC and two specific regions within Ssb characterized by positive charges. The C-terminus of Ssb mediates the key contact and a second attachment point is provided by a KRR-motif in the substrate binding domain. Strikingly, ribosome binding of Ssb is not essential. Autonomous ribosome attachment becomes necessary if RAC is absent, suggesting a dual mode of Ssb recruitment to nascent chains. We propose, that the multilayered ribosomal interaction allows positioning of Ssb in an optimal orientation to the tunnel exit guaranteeing an efficient nascent polypeptide interaction.
authors.affiliation: Department of Biology, Molecular Microbiology, University of Konstanz, 78457 Konstanz, Germany.|Konstanz Research School Chemical Biology, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Marie A
authors.initials: MA
authors.lastname: Hanebuth
authors.affiliation: Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Kityk
authors.affiliation: Department of Biology, Molecular Microbiology, University of Konstanz, 78457 Konstanz, Germany.|Konstanz Research School Chemical Biology, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Fries
authors.affiliation: Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Alok
authors.initials: A
authors.lastname: Jain
authors.affiliation: Department of Biology, Stanford University, Stanford, California 94305-5430, USA.
authors.forename: Allison
authors.initials: A
authors.lastname: Kriel
authors.affiliation: Department of Biology, Stanford University, Stanford, California 94305-5430, USA.
authors.forename: Veronique
authors.identifier: http://orcid.org/0000-0002-5947-7415
authors.initials: V
authors.lastname: Albanese
authors.affiliation: Department of Biology, Applied Bioinformatics, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Tancred
authors.initials: T
authors.lastname: Frickey
authors.affiliation: Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Peter
authors.affiliation: Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany.
authors.forename: Matthias P
authors.identifier: http://orcid.org/0000-0002-7859-3112
authors.initials: MP
authors.lastname: Mayer
authors.affiliation: Department of Biology, Stanford University, Stanford, California 94305-5430, USA.
authors.forename: Judith
authors.identifier: http://orcid.org/0000-0003-2302-6943
authors.initials: J
authors.lastname: Frydman
authors.affiliation: Department of Biology, Molecular Microbiology, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Deuerling
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D003198:Computer Simulation; D017124:Conserved Sequence; D005816:Genetic Complementation Test; D058685:Genetic Pleiotropy; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D010455:Peptides / Q000378:metabolism*; D010641:Phenotype; D011485:Protein Binding; D012270:Ribosomes / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D018840:HSP70 Heat-Shock Proteins; D010455:Peptides; C095192:SSB1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins