An atomic model AAA-ATPase/20S core particle sub-complex of the 26S proteasome

Abstract

The 26S proteasome is the most downstream element of the ubiquitin–proteasome pathway of protein degradation. It is composed of the 20S core particle (CP) and the 19S regulatory particle (RP). The RP consists of 6 AAA-ATPases and at least 13 non-ATPase subunits. Based on a cryo-EM map of the 26S proteasome, structures of homologs, and physical protein–protein interactions we derive an atomic model of the AAA-ATPase–CP sub-complex. The ATPase order in our model (Rpt1/Rpt2/Rpt6/Rpt3/Rpt4/Rpt5) is in excellent agreement with the recently identified base–precursor complexes formed during the assembly of the RP. Furthermore, the atomic CP–AAA-ATPase model suggests that the assembly chaperone Nas6 facilitates CP–RP association by enhancing the shape complementarity between Rpt3 and its binding CP alpha subunits partners.