Proteasome assembly from 15S precursors involves major conformational changes and recycling of the Pba1-Pba2 chaperone

The barrel-shaped 20S proteasome core particle assembles via 15S intermediates through the action of Ump1 and Pba1–Pba2 chaperones. Using structural approaches, Kock et al. reveal conformational changes occurring upon formation of the nascent 20S particle leading to ejection of Pba1–Pba2.