Targeted delivery of an ssrA-tagged substrate by the adaptor protein SspB to its cognate AAA+ protein ClpX |
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Authors: | Dougan David A Weber-Ban Eilika Bukau Bernd |
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Institution: | Zentrum für Molekulare Biologie Heidelberg, Universit?t Heidelberg, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany. d.dougan@zmbh.uni-heidelberg.de |
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Abstract: | In the bacterial cytosol, degradation of ssrA-tagged proteins is primarily carried out by the proteolytic machine ClpXP in a process which is stimulated by a ClpX-specific adaptor protein, SspB. Here we elucidate the steps required for binding and transfer of ssrA-tagged substrates from SspB to ClpX. The N-terminal region of SspB is essential for its interaction with ssrA-tagged substrates, while a short conserved region at the C terminus of SspB interacts specifically with the N domain of ClpX. A single point mutation within the conserved C-terminal region of SspB is sufficient to abolish the SspB-mediated degradation of ssrA-tagged proteins by ClpXP. We propose that this region represents a common motif for the recognition of ClpX as the C-terminal region of SspB shares considerable homology with the other ClpX-specific adaptor protein, RssB. Through docking of SspB to the N-terminal domain of ClpX, the substrate is delivered to the substrate binding site in ClpX. |
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