19S proteasome/PA700

The 19S regulatory particle (PA700) locates on either one or both ends of the 20S core particle of the 26S proteasome. It has 19 subunits including six AAA ATPases that associate with α subunits of the 20S proteasome to form the 26S proteasome. PA700 plays an essential role in preparing substrate proteins to be degraded by the 20S proteasome, including binding, deubiquitinating and unfolding polyubiquitinated proteins.