2.3. 19S regulatory particle and 26S/30S proteasomes

Degradation of ub-labeled proteasome substrates depends on 26S/30S proteasomes. These protease complexes contain either one or two 19S regulatory particles (RP) associated with the α-ring subunits of s20S or i20S CPs. The 19S RP (proteasome activator PA700) is composed of base and lid sub-complexes that reveal defined pathways of chaperone-assisted assembly [9]. The base ATPase sub-complex (subunits Rpt1–Rpt6) harbors a chaperon-like unfoldase activity [24] and is involved in substrate channeling into 26S or 30S proteasomes. The lid sub-complex enables ub-conjugate binding, as well as deubiquitination for ubiquitin recycling and substrate channeling. Assembly, composition, and topology, as well as specific biological aspects of 26S/30S proteasome genesis and function, have been reviewed comprehensively by others [20, 25, 26].
