Unfolding and internalization of proteins by the ATP-dependent proteases ClpXP and ClpAP. Export

@article{citeulike:1045465, abstract = {ClpX and ClpA are molecular chaperones that interact with specific proteins and, together with ClpP, activate their ATP-dependent degradation. The chaperone activity is thought to convert proteins into an extended conformation that can access the sequestered active sites of ClpP. We now show that ClpX can catalyze unfolding of a green fluorescent protein fused to a ClpX recognition motif (GFP-SsrA). Unfolding of GFP-SsrA depends on ATP hydrolysis. GFP-SsrA unfolded either by ClpX or by treatment with denaturants binds to ClpX in the presence of adenosine 5'-O-(3-thiotriphosphate) and is released slowly (t(1/2) approximately 15 min). Unlike ClpA, ClpX cannot trap unfolded proteins in stable complexes unless they also have a high-affinity binding motif. Addition of ATP or ADP accelerates release (t(1/2) approximately 1 min), consistent with a model in which ATP hydrolysis induces a conformation of ClpX with low affinity for unfolded substrates. Proteolytically inactive complexes of ClpXP and ClpAP unfold GFP-SsrA and translocate the protein to ClpP, where it remains unfolded. Complexes of ClpXP with translocated substrate within the ClpP chamber retain the ability to unfold GFP-SsrA. Our results suggest a bipartite mode of interaction between ClpX and substrates. ClpX preferentially targets motifs exposed in specific proteins. As the protein is unfolded by ClpX, additional motifs are exposed that facilitate its retention and favor its translocation to ClpP for degradation.}, address = {Laboratory of Cell Biology and Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.}, author = {Singh, S. K. and Grimaud, R. and Hoskins, J. R. and Wickner, S. and Maurizi, M. R.}, citeulike-article-id = {1045465}, citeulike-linkout-0 = {http://view.ncbi.nlm.nih.gov/pubmed/10922052}, citeulike-linkout-1 = {http://www.hubmed.org/display.cgi?uids=10922052}, day = {1}, issn = {0027-8424}, journal = {Proc Natl Acad Sci U S A}, keywords = {chaperone, protein-degradation, protein-translocation}, month = {August}, number = {16}, pages = {8898--8903}, posted-at = {2007-01-17 08:20:55}, priority = {2}, title = {Unfolding and internalization of proteins by the ATP-dependent proteases ClpXP and ClpAP.}, url = {http://view.ncbi.nlm.nih.gov/pubmed/10922052}, volume = {97}, year = {2000} }

TY - JOUR ID - citeulike:1045465 L3 - citeulike-article-id:1045465 N2 - ClpX and ClpA are molecular chaperones that interact with specific proteins and, together with ClpP, activate their ATP-dependent degradation. The chaperone activity is thought to convert proteins into an extended conformation that can access the sequestered active sites of ClpP. We now show that ClpX can catalyze unfolding of a green fluorescent protein fused to a ClpX recognition motif (GFP-SsrA). Unfolding of GFP-SsrA depends on ATP hydrolysis. GFP-SsrA unfolded either by ClpX or by treatment with denaturants binds to ClpX in the presence of adenosine 5'-O-(3-thiotriphosphate) and is released slowly (t(1/2) approximately 15 min). Unlike ClpA, ClpX cannot trap unfolded proteins in stable complexes unless they also have a high-affinity binding motif. Addition of ATP or ADP accelerates release (t(1/2) approximately 1 min), consistent with a model in which ATP hydrolysis induces a conformation of ClpX with low affinity for unfolded substrates. Proteolytically inactive complexes of ClpXP and ClpAP unfold GFP-SsrA and translocate the protein to ClpP, where it remains unfolded. Complexes of ClpXP with translocated substrate within the ClpP chamber retain the ability to unfold GFP-SsrA. Our results suggest a bipartite mode of interaction between ClpX and substrates. ClpX preferentially targets motifs exposed in specific proteins. As the protein is unfolded by ClpX, additional motifs are exposed that facilitate its retention and favor its translocation to ClpP for degradation. IS - 16 JF - Proc Natl Acad Sci U S A SN - 0027-8424 AD - Laboratory of Cell Biology and Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA. EP - 8903 TI - Unfolding and internalization of proteins by the ATP-dependent proteases ClpXP and ClpAP. VL - 97 SP - 8898 KW - chaperone KW - protein-degradation KW - protein-translocation AU - Singh, SK AU - Grimaud, R AU - Hoskins, JR AU - Wickner, S AU - Maurizi, MR PY - 2000/08/01/ UR - http://view.ncbi.nlm.nih.gov/pubmed/10922052 ER -