7e55
From Proteopedia
Cryo-EM structure of alpha 7 homo-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 proteasome, which is composed of layered alpha and beta heptameric rings, is the core complex of the eukaryotic proteasome involved in proteolysis. The alpha7 subunit is a component of the alpha ring, and it self-assembles into a homo-tetradecamer consisting of two layers of alpha7 heptameric rings. However, the structure of the alpha7 double ring in solution has not been fully elucidated. We applied cryo-electron microscopy to delineate the structure of the alpha7 double ring in solution, revealing a structure different from the previously reported crystallographic model. The D7-symmetrical double ring was stacked with a 15 degrees clockwise twist and a separation of 3 A between the two rings. Two more conformations, dislocated and fully open, were also identified. Our observations suggest that the alpha7 double-ring structure fluctuates considerably in solution, allowing for the insertion of homologous alpha subunits, finally converting to the hetero-heptameric alpha rings in the 20S proteasome. Structural Fluctuations of the Human Proteasome alpha7 Homo-Tetradecamer Double Ring Imply the Proteasomal alpha-Ring Assembly Mechanism.,Song C, Satoh T, Sekiguchi T, Kato K, Murata K Int J Mol Sci. 2021 Apr 26;22(9). pii: ijms22094519. doi: 10.3390/ijms22094519. PMID:33926037[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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