Structural basis of SspB-tail recognition by the zinc binding domain of ClpX.
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 A resolution in each different crystal form and also in complex with XB peptide at 1.6 A resolution. The XB peptide forms an antiparallel beta-sheet with two beta-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.
Park
Eun Young
EY
School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.
Lee
Byung-Gil
BG
Hong
Seung-Beom
SB
Kim
Hyung-Wook
HW
Jeon
Hyesung
H
Song
Hyun Kyu
HK
D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D049071:Endopeptidase Clp / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D013379:Substrate Specificity; D015032:Zinc / Q000737:chemistry*
D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D011993:Recombinant Fusion Proteins; C477700:sspB protein, E coli; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities; D015032:Zinc