Structure of the AAA ATPase p97

p97, an abundant hexameric ATPase of the AAA family, is involved in homotyp ic membrane fusion. It is thought to disassemble SNARE complexes formed dur ing the process of membrane fusion. Here, we report two structures: a cryst al structure of the N-terminal and D1 ATPase domains of murine p97 at 2.9 A ngstrom resolution, and a cryoelectron microscopy structure of full-length rat p97 at 18 Angstrom resolution. Together, these structures show that the D1 and D2 hexamers pack in a tail-to-tail arrangement, and that the N doma in is flexible. A comparison with NSF D2 (ATP complex) reveals possible con formational changes induced by ATP hydrolysis. Given the D1 and D2 packing arrangement, we propose a ratchet mechanism for p97 during its ATP hydrolys is cycle.