5ofo
From Proteopedia
Cryo EM structure of the E. coli disaggregase ClpB (BAP form, DWB mutant), in the ATPgammaS state, bound to the model substrate casein
Structural highlights
Function[CLPB_ECOLI] Part of a stress-induced multi-chaperone system, it is involved in the recovery of the cell from heat-induced damage, in cooperation with DnaK, DnaJ and GrpE. Acts before DnaK, in the processing of protein aggregates. Protein binding stimulates the ATPase activity; ATP hydrolysis unfolds the denatured protein aggregates, which probably helps expose new hydrophobic binding sites on the surface of ClpB-bound aggregates, contributing to the solubilization and refolding of denatured protein aggregates by DnaK.[1] [2] [3] Publication Abstract from PubMedRefolding aggregated proteins is essential in combating cellular proteotoxic stress. Together with Hsp70, Hsp100 chaperones, including Escherichia coli ClpB, form a powerful disaggregation machine that threads aggregated polypeptides through the central pore of tandem adenosine triphosphatase (ATPase) rings. To visualize protein disaggregation, we determined cryo-electron microscopy structures of inactive and substrate-bound ClpB in the presence of adenosine 5'-O-(3-thiotriphosphate), revealing closed AAA+ rings with a pronounced seam. In the substrate-free state, a marked gradient of resolution, likely corresponding to mobility, spans across the AAA+ rings with a dynamic hotspot at the seam. On the seam side, the coiled-coil regulatory domains are locked in a horizontal, inactive orientation. On the opposite side, the regulatory domains are accessible for Hsp70 binding, substrate targeting, and activation. In the presence of the model substrate casein, the polypeptide threads through the entire pore channel and increased nucleotide occupancy correlates with higher ATPase activity. Substrate-induced domain displacements indicate a pathway of regulated substrate transfer from Hsp70 to the ClpB pore, inside which a spiral of loops contacts the substrate. The seam pore loops undergo marked displacements, along with ordering of the regulatory domains. These asymmetric movements suggest a mechanism for ATPase activation and substrate threading during disaggregation. Structural pathway of regulated substrate transfer and threading through an Hsp100 disaggregase.,Deville C, Carroni M, Franke KB, Topf M, Bukau B, Mogk A, Saibil HR Sci Adv. 2017 Aug 4;3(8):e1701726. doi: 10.1126/sciadv.1701726. eCollection 2017 , Aug. PMID:28798962[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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Categories: Bukau, B | Carroni, M | Deville, C | Franke, K B | Mogk, A | Saibil, H R | Topf, M | Aaa | Chaperone | Clpb | Disaggregase
