Interaction of the cotranslational Hsp70 Ssb with ribosomal proteins and rRNA depends on its lid domain.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 27882919.
- Also identified by DOI 10.1038/ncomms13563 and PMC identifier 5123055.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
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.
Medical subject headings
- GTP-Binding Proteins
- HSP70 Heat-Shock Proteins
- Peptide Elongation Factors
- Protein Conformation, alpha-Helical
- RNA, Ribosomal
- Ribosomal Proteins
- Saccharomyces cerevisiae Proteins