RAC, a stable ribosome-associated complex in yeast formed by the DnaK-DnaJ homologs Ssz1p and zuotin

Matthias Gautschi, Hauke Lilie, Ursula Funfschilling, Andrej Mun, Suzanne Ross, Trevor James Lithgow, Peter Rucknagel, Sabine Rospert

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154 Citations (Scopus)


The yeast cytosol contains multiple homologs of the DnaK and DnaJ chaperone family. Our current understanding of which homologs functionally interact is incomplete. Zuotin is a DnaJ homolog bound to the yeast ribosome. We have now identified the DnaK homolog Ssz1p/Pdr13p as zuotin s partner chaperone. Zuotin and Ssz1p form a ribosome-associated complex (RAC) that is bound to the ribosome via the zuotin subunit. RAC is unique among the eukaryotic DnaK-DnaJ systems, as the 1:1 complex is stable, even in the presence of ATP or ADP. In vitro, RAC stimulates the translocation of a ribosome-bound mitochondrial precursor protein into mitochondria, providing evidence for its chaperone-like effect on nascent chains. In agreement with the existence of a functional complex, deletion of each RAC subunit resulted in a similar phenotype in vivo. However, overexpression of zuotin partly rescued the growth defect of the Delta ssz1 strain, whereas overexpression of Ssz1p did not affect the Delta zuo1 strain, suggesting a pivotal function for the DnaJ homolog.
Original languageEnglish
Pages (from-to)3762 - 3767
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number7
Publication statusPublished - 2001

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