What's the Key to Unlocking the Proteasome's Gate?

In this issue of Structure, Bolten et al. (2016) describe the organization of the mycobacterial proteasome in complex with the ATP-independent bacterial proteasome activator (Bpa, PafE). They confirm several activation motifs employed by archaea and eukaryotes and highlight differences that pose Bpa as a novel architectural class of proteasome activators.