8cxb | pdb_00008cxb
Human PA28-20S (PA28-4a3b)
Structural highlights
FunctionPSA7_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. Plays an important role in the regulation of cell proliferation or cell cycle control, transcriptional regulation, immune and stress response, cell differentiation, and apoptosis. Interacts with some important proteins involved in transcription factor regulation, cell cycle transition, viral replication and even tumor initiation and progression. Inhibits the transactivation function of HIF-1A under both normoxic and hypoxia-mimicking conditions. The interaction with EMAP2 increases the proteasome-mediated HIF-1A degradation under the hypoxic conditions. Plays a role in hepatitis C virus internal ribosome entry site-mediated translation. Mediates nuclear translocation of the androgen receptor (AR) and thereby enhances androgen-mediated transactivation. Promotes MAVS degradation and thereby negatively regulates MAVS-mediated innate immune response.[1] [2] [3] [4] [5] Publication Abstract from PubMedThe ability to produce folded and functional proteins is a necessity for structural biology and many other biological sciences. This task is particularly challenging for numerous biomedically important targets in human cells, including membrane proteins and large macromolecular assemblies, hampering mechanistic studies and drug development efforts. Here we describe a method combining CRISPR-Cas gene editing and fluorescence-activated cell sorting to rapidly tag and purify endogenous proteins in HEK cells for structural characterization. We applied this approach to study the human proteasome from HEK cells and rapidly determined cryogenic electron microscopy structures of major proteasomal complexes, including a high-resolution structure of intact human PA28alphabeta-20S. Our structures reveal that PA28 with a subunit stoichiometry of 3alpha/4beta engages tightly with the 20S proteasome. Addition of a hydrophilic peptide shows that polypeptides entering through PA28 are held in the antechamber of 20S prior to degradation in the proteolytic chamber. This study provides critical insights into an important proteasome complex and demonstrates key methodologies for the tagging of proteins from endogenous sources. Structural insights into the human PA28-20S proteasome enabled by efficient tagging and purification of endogenous proteins.,Zhao J, Makhija S, Zhou C, Zhang H, Wang Y, Muralidharan M, Huang B, Cheng Y Proc Natl Acad Sci U S A. 2022 Aug 16;119(33):e2207200119. doi:, 10.1073/pnas.2207200119. Epub 2022 Jul 19. PMID:35858375[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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