title: Functional characterization of the atypical Hsp70 subunit of yeast ribosome-associated complex.
abstract: Eukaryotic ribosomes carry a stable chaperone complex termed ribosome-associated complex consisting of the J-domain protein Zuo1 and the Hsp70 Ssz1. Zuo1 and Ssz1 together with the Hsp70 homolog Ssb1/2 form a functional triad involved in translation and early polypeptide folding processes. Strains lacking one of these components display slow growth, cold sensitivity, and defects in translational fidelity. Ssz1 diverges from canonical Hsp70s insofar that neither the ability to hydrolyze ATP nor binding to peptide substrates is essential in vivo. The exact role within the chaperone triad and whether or not Ssz1 can hydrolyze ATP has remained unclear. We now find that Ssz1 is not an ATPase in vitro, and even its ability to bind ATP is dispensable in vivo. Furthermore, Ssz1 function was independent of ribosome-associated complex formation, indicating that Ssz1 is not merely a structural scaffold for Zuo1. Finally, Ssz1 function in vivo was inactivated when both nucleotide binding and Zuo1 interaction via the C-terminal domain were disrupted in the same mutant. The two domains of this protein thus cooperate in a way that allows for severe interference in either but not in both of them.
authors: Institute of Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Zellforschung (ZBMZ), University of Freiburg, Herrmann-Herder-Strasse 7, Freiburg, Germany.
authors: Charlotte
authors: C
authors: Conz
authors: Hendrik
authors: H
authors: Otto
authors: Kristin
authors: K
authors: Peisker
authors: Matthias
authors: M
authors: Gautschi
authors: Tina
authors: T
authors: Wölfle
authors: Matthias P
authors: MP
authors: Mayer
authors: Sabine
authors: S
authors: Rospert
mesh_terms: D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding / Q000235:genetics; D014176:Protein Biosynthesis / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; C095192:SSB1 protein, S cerevisiae; C424445:SSZ1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C077019:ZUO1 protein, S cerevisiae; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C494470:SSB2 protein, S cerevisiae