Abstract
In prokaryotes, incomplete or misfolded polypeptides emanating from a stalled ribosome are marked for degradation by the addition of an 11 residue peptide (AANDENYALAA) to their C terminus. Substrates containing this conserved degradation signal, the SsrA tag, are targeted to specific proteases including ClpXP and ClpAP. SspB was originally characterized as a stringent starvation protein and has been found to bind specifically to SsrA-tagged proteins and to enhance recognition of these proteins by the ClpXP degradation machine. Here, we report the crystal structures of SspB alone and in complex with an SsrA peptide. Unexpectedly, SspB exhibits a fold found in Sm-family RNA binding proteins. The dimeric SspB structures explain the key determinants for recognition of the SsrA tag and define a hydrophobic channel that may bind unfolded substrates.
| Original language | English |
|---|---|
| Pages (from-to) | 75-86 |
| Number of pages | 12 |
| Journal | Molecular Cell |
| Volume | 12 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 2003 Jul 1 |
| Externally published | Yes |
Bibliographical note
Funding Information:We thank Dr. P.W. Kim for assistance with the ITC experiments and the staff at F1 beamline, MacCHESS and X12C beamline, NSLS, BNL for help with data collection. We also thank Drs. P. Zwickl (Max-Planck-Institute for Biochemistry, Germany) and T. Tamura (National Institute of Advanced Industrial Science and Technology, Japan) for cells containing His-GFP-SsrA and Prof. R. Huber for his generous support in the initial stage of this project. This work was supported in part by a grant from the National Institutes of Health (M.J.E.). M.J.E. is a recipient of a Scholar Award from the Leukemia and Lymphoma Society.
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology