Structural basis of SspB-tail recognition by the zinc binding domain of ClpX |
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Authors: | Park Eun Young Lee Byung-Gil Hong Seung-Beom Kim Hyung-Wook Jeon Hyesung Song Hyun Kyu |
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Affiliation: | School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea. |
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Abstract: | 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. |
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Keywords: | SspB-CHis, carboxy-terminal histidine tagged SspB protein SspB-ClpX, SspB and ClpX fusion protein SspB-ZBD, SspB and zinc binding domain of ClpX fusion protein XB, ClpX-binding motif in SspB ZBD, zinc binding domain of ClpX |
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