Biology subjects

Gates, S. N.

Publications and source records attributed to Gates, S. N..

2 recordsLinked to original sources

bioRxiv2018

Structural basis for substrate gripping and translocation by the ClpB AAA+ disaggregase

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 [A] resolution bound to the model substrate, casein in the presence of slowly hydrolysable ATP{gamma}S. 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.

biophysics↗

bioRxiv2018

Structures of the substrate-engaged 26S proteasome reveal the mechanisms for ATP hydrolysis-driven translocation

The 26S proteasome is the primary eukaryotic degradation machine and thus critically involved in numerous cellular processes. The hetero-hexameric ATPase motor of the proteasome unfolds and translocates targeted protein substrates into the open gate of a proteolytic core, while a proteasomal deubiquitinase concomitantly removes substrate-attached ubiquitin chains. However, the mechanisms by which ATP hydrolysis drives the conformational changes responsible for these processes have remained elusive. Here we present the cryo-EM structures of four distinct conformational states of the actively ATP-hydrolyzing, substrate-engaged 26S proteasome. These structures reveal how mechanical substrate translocation accelerates deubiquitination, and how ATP-binding, hydrolysis, and phosphate-release events are coordinated within the AAA+ motor to induce conformational changes and propel the substrate through the central pore.

molecular biology↗