The conformational landscape of the AAA+-ATPase of the 26S proteasome studied by cryo-electron microscopy

In eukaryotic cells selective protein degradation is mediated by the 26S proteasome. The proteasomal AAA+-ATPase unfolds substrates into the core particle, where proteolysis takes place. Applying single-particle cryo-electron microscopy and image classification to samples in the presence of different nucleotides and nucleotide analogs, we were able to observe four distinct conformational states. In a hitherto unobserved state (s4) the gate of the core particle is open. The resolution of the four conformers allowed for the construction of atomic models of the AAA+-ATPase module as it progresses through the functional cycle.