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A functional chaperone triad on the yeast ribosome.

The chaperones RAC (ribosome-associated complex), consisting of Ssz1p and zuotin, and Ssb1/2p are associated with ribosomes of yeast. Ssb1/2p was previously shown to form a crosslink product to polypeptides trapped in ribosome-nascent chain complexes (RNCs) in vitro. Here we show that an efficient crosslink of the nascent chain to Ssb1/2p depends on the presence of functional RAC. The crosslink to Ssb1/2p was significantly diminished if (i) RAC was removed from RNCs: a process reversed by addition of purified RAC; (ii) RAC carried a mutation in the J-domain of zuotin, leading to its inactivation in vivo; (iii) RAC's Ssz1p subunit was absent because RNCs were generated in a Deltassz1-derived translation extract. In vivo the same specific set of growth defects caused by the absence of any of the three chaperones was also displayed by a Deltassb1/2Deltassz1Deltazuo1 strain. The combination of in vitro and in vivo data supports a model in which Ssb1/2p, Ssz1p, and zuotin act in concert on nascent chains while they are being synthesized.

Pubmed ID: 11929994

Authors

  • Gautschi M
  • Mun A
  • Ross S
  • Rospert S

Journal

Proceedings of the National Academy of Sciences of the United States of America

Publication Data

April 2, 2002

Associated Grants

None

Mesh Terms

  • DNA-Binding Proteins
  • Fungal Proteins
  • HSP70 Heat-Shock Proteins
  • Molecular Chaperones
  • Ribosomes
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Schizosaccharomyces pombe Proteins