Two-step process for disassembly mechanism of proteasome ?7 homo-tetradecamer by ?6 revealed by high-speed atomic force microscopy.

ABSTRACT: The 20S proteasome is a core particle of the eukaryotic proteasome responsible for proteolysis and is composed of layered ? and ? hetero-heptameric rings. The ?7 subunit, which is one of components of the ? ring, is known to self-assemble into a double-ringed homo-tetradecamer composed of two layers of the ?7 heptameric ring. The ?7 tetradecamer is known to disassemble upon the addition of ?6 subunit, producing a 1:7 hetero-octameric ?6-?7 complex. However, the detailed disassembly mechanism remains unclear. Here, we applied high-speed atomic force microscopy (HS-AFM) to dissect the disassembly process of the ?7 double ring caused by interaction with the ?6. HS-AFM movies clearly demonstrated two different modes of interaction in which the ?6 monomer initially cracks at the interface between the stacked two ?7 single rings and the subsequent intercalation of the ?6 monomer in the open pore of the ?7 single ring blocks the re-association of the single rings into the double ring. This result provides a mechanistic insight about the disassembly process of non-native homo-oligomers formed by proteasome components which is crucial for the initial process for assembly of 20S proteasome.

SUBMITTER: Kozai T 

PROVIDER: S-EPMC5684232 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature