The 26S proteasome is involved in the ATP-dependent degradation of ubiquitinated proteins. The regulatory (or ATPase) complex confers ATP dependency and substrate specificity to the 26S complex. Found in the multi-protein complexes: the 26S proteasome (formed from the 20S proteasome and PA700), and the modulator. PA700 consists of 28 subunits arranged to form a cylinder-shaped complex by four stacked rings, each containing seven subunits. Interacts with PAAF1 (By similarity). Belongs to the AAA ATPase family.