Structural Basis of SspB-tail Recognition by the Zinc Binding Domain of ClpX

Eun Young Park, Byung Gil Lee, Seung Beom Hong, Hyung Wook Kim, Hyesung Jeon, Hyun Kyu Song

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)


The degradation of ssrA(AANDENYALAA)-tagged proteins in the bacterial cytosol is carried out by the ClpXP protease and is markedly stimulated by the SspB adaptor protein. It has previously been reported that the amino-terminal zinc-binding domain of ClpX (ZBD) is involved in complex formation with the SspB-tail (XB: ClpX-binding motif). In an effort to better understand the recognition of SspB by ClpX and the mechanism of delivery of ssrA-tagged substrates to ClpXP, we have determined the structures of ZBD alone at 1.5, 2.0, and 2.5 Å resolution in each different crystal form and also in complex with XB peptide at 1.6 Å resolution. The XB peptide forms an antiparallel β-sheet with two β-strands of ZBD, and the structure shows a 1:1 stoichiometric complex between ZBD and XB, suggesting that there are two independent SspB-tail-binding sites in ZBD. The high-resolution ZBD:XB complex structure, in combination with biochemical analyses, can account for key determinants in the recognition of the SspB-tail by ClpX and sheds light on the mechanism of delivery of target proteins to the prokaryotic degradation machine.

Original languageEnglish
Pages (from-to)514-526
Number of pages13
JournalJournal of Molecular Biology
Issue number2
Publication statusPublished - 2007 Mar 23

Bibliographical note

Funding Information:
We thank the staff at 4A beamline, Pohang Accelerator Laboratory, Republic of Korea and NW12 beamline, Photon Factory, Japan 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 Professor M. J. Eck for his generous support during the initial stage of this project. This work was supported by the Korea Research Foundation Grant (KRF-2006-312-C00249) funded by the Korean Government (MOEHRD) and by the Korea Science and Engineering Foundation Grant (KOSEF, R01-2004-000-10773-0) funded by the Korea government (MOST). E.Y.P. was supported by a Seoul Science Fellowship.


  • ATP-dependent protease
  • ClpXP
  • crystal
  • delivery complex
  • ssrA tag

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Molecular Biology


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