Disassembly of the self-assembled, double-ring structure of proteasome ?7 homo-tetradecamer by ?6.

ABSTRACT: The 20S core particle of the eukaryotic proteasome is composed of two ?- and two ?-rings, each of which is a hetero-heptamer composed of seven homologous but distinct subunits. Although formation of the eukaryotic proteasome is a highly ordered process assisted by assembly chaperones, ?7, an ?-ring component, has the unique property of self-assembling into a homo-tetradecamer. We used biophysical methods to characterize the oligomeric states of this proteasome subunit and its interaction with ?6, which makes direct contacts with ?7 in the proteasome ?-ring. We determined a crystal structure of the ?7 tetradecamer, which has a double-ring structure. Sedimentation velocity analytical ultracentrifugation and mass spectrometric analysis under non-denaturing conditions revealed that ?7 exclusively exists as homo-tetradecamer in solution and that its double-ring structure is disassembled upon the addition of ?6, resulting in a 1:7 hetero-octameric ?6-?7 complex. Our findings suggest that proteasome formation involves the disassembly of non-native oligomers, which are assembly intermediates.

SUBMITTER: Ishii K 

PROVIDER: S-EPMC4677347 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature