ジャーナル: Nat Commun / 年: 2021 タイトル: The 20S as a stand-alone proteasome in cells can degrade the ubiquitin tag. 著者: Indrajit Sahu / Sachitanand M Mali / Prasad Sulkshane / Cong Xu / Andrey Rozenberg / Roni Morag / Manisha Priyadarsini Sahoo / Sumeet K Singh / Zhanyu Ding / Yifan Wang / Sharleen Day / Yao ...著者: Indrajit Sahu / Sachitanand M Mali / Prasad Sulkshane / Cong Xu / Andrey Rozenberg / Roni Morag / Manisha Priyadarsini Sahoo / Sumeet K Singh / Zhanyu Ding / Yifan Wang / Sharleen Day / Yao Cong / Oded Kleifeld / Ashraf Brik / Michael H Glickman / 要旨: The proteasome, the primary protease for ubiquitin-dependent proteolysis in eukaryotes, is usually found as a mixture of 30S, 26S, and 20S complexes. These complexes have common catalytic sites, ...The proteasome, the primary protease for ubiquitin-dependent proteolysis in eukaryotes, is usually found as a mixture of 30S, 26S, and 20S complexes. These complexes have common catalytic sites, which makes it challenging to determine their distinctive roles in intracellular proteolysis. Here, we chemically synthesize a panel of homogenous ubiquitinated proteins, and use them to compare 20S and 26S proteasomes with respect to substrate selection and peptide-product generation. We show that 20S proteasomes can degrade the ubiquitin tag along with the conjugated substrate. Ubiquitin remnants on branched peptide products identified by LC-MS/MS, and flexibility in the 20S gate observed by cryo-EM, reflect the ability of the 20S proteasome to proteolyze an isopeptide-linked ubiquitin-conjugate. Peptidomics identifies proteasome-trapped ubiquitin-derived peptides and peptides of potential 20S substrates in Hi20S cells, hypoxic cells, and human failing-heart. Moreover, elevated levels of 20S proteasomes appear to contribute to cell survival under stress associated with damaged proteins.