1OX9: Crystal Structure Of Sspb-Ssra Complex

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.
PDB ID: 1OX9Download
MMDB ID: 24017
PDB Deposition Date: 2003/4/1
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 2.9  Å
Source Organism:
Escherichia coli O157:H7
Similar Structures:
Biological Unit for 1OX9: tetrameric; determined by author and by software (PISA)
Molecular Components in 1OX9
Label Count Molecule
Proteins (4 molecules)
Stringent Starvation Protein B
Molecule annotation
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB