Structural basis for substrate gripping and translocation by the ClpB AAA+ disaggregase
Alexandrea N. Rizo, JiaBei Lin, Stephanie N. Gates, Eric Tse, Stephen M. Bart, Laura M. Castellano, Frank DiMaio, James Shorter, and Daniel R. Southworth
Received Date: 21st September 2018
Bacterial ClpB and yeast Hsp104 are homologous Hsp100 protein disaggregases that serve critical functions in proteostasis by solubilizing protein aggregates. Two AAA+ nucleotide binding domains (NBDs) power polypeptide translocation through a central channel comprised of a hexameric spiral of protomers that contact substrate via conserved pore-loop interactions. To elucidate the translocation mechanism, we determined the cryo-EM structure of a hyperactive ClpB variant to 2.9 Å resolution bound to the model substrate, casein in the presence of slowly hydrolysable ATPγS. Distinct substrate-gripping mechanisms are identified for NBD1 and NBD2 pore loops. A trimer of N-terminal domains define a channel entrance that binds the polypeptide substrate adjacent the topmost NBD1 contact. NBD conformations at the spiral seam reveal how ATP hydrolysis and substrate engagement or disengagement are precisely tuned to drive a stepwise translocation cycle.
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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.