Characterization of the N-terminal repeat domain of Escherichia coli ClpA-A class I Clp/HSP100 ATPase |
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Authors: | Lo J H Baker T A Sauer R T |
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Institution: | Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. |
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Abstract: | The ClpA, ClpB, and ClpC subfamilies of the Clp/HSP100 ATPases contain a conserved N-terminal region of approximately 150 residues that consists of two approximate sequence repeats. This sequence from the Escherichia coli ClpA enzyme is shown to encode an independent structural domain (the R domain) that is monomeric and approximately 40% alpha-helical. A ClpA fragment lacking the R domain showed ATP-dependent oligomerization, protein-stimulated ATPase activity, and the ability to complex with the ClpP peptidase and mediate degradation of peptide and protein substrates, including casein and ssrA-tagged proteins. Compared with the activities of the wild-type ClpA, however, those of the ClpA fragment missing the R domain were reduced. These results indicate that the R domain is not required for the basic recognition, unfolding, and translocation functions that allow ClpA-ClpP to degrade some protein substrates, but they suggest that it may play a role in modulating these activities. |
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Keywords: | ATP-dependent protein degradation disassembly chaperone ssrA-tagged substrates ClpP ClpA65 |
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