5dsv | pdb_00005dsv
Crystal structure of human proteasome alpha7 tetradecamer
Structural highlights
Function[PSA3_HUMAN] The proteasome is a multicatalytic proteinase complex which is characterized by its ability to cleave peptides with Arg, Phe, Tyr, Leu, and Glu adjacent to the leaving group at neutral or slightly basic pH. The proteasome has an ATP-dependent proteolytic activity. Binds to the C-terminus of CDKN1A and thereby mediates its degradation. Negatively regulates the membrane trafficking of the cell-surface thromboxane A2 receptor (TBXA2R) isoform 2.[1] [2] Publication Abstract from PubMedThe 20S core particle of the eukaryotic proteasome is composed of two alpha- and two beta-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, alpha7, an alpha-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 alpha6, which makes direct contacts with alpha7 in the proteasome alpha-ring. We determined a crystal structure of the alpha7 tetradecamer, which has a double-ring structure. Sedimentation velocity analytical ultracentrifugation and mass spectrometric analysis under non-denaturing conditions revealed that alpha7 exclusively exists as homo-tetradecamer in solution and that its double-ring structure is disassembled upon the addition of alpha6, resulting in a 1:7 hetero-octameric alpha6-alpha7 complex. Our findings suggest that proteasome formation involves the disassembly of non-native oligomers, which are assembly intermediates. Disassembly of the self-assembled, double-ring structure of proteasome alpha7 homo-tetradecamer by alpha6.,Ishii K, Noda M, Yagi H, Thammaporn R, Seetaha S, Satoh T, Kato K, Uchiyama S Sci Rep. 2015 Dec 14;5:18167. doi: 10.1038/srep18167. PMID:26657688[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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