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OTU (ovarian tumor) domain of ubiquitin thioesterase OTU1 and similar proteins Ubiquitin thioesterase (EC 3.4.19.12) OTU1 is also called OTU domain-containing protein 1 in yeast, while human OTU1 is also called HIV-1-induced protease 7 (HIN7), DUBA-8, or OTU domain-containing protein 2 (OTUD2). OTU1 is a deubiquitinase (DUB) that catalyzes the thiol-dependent hydrolysis of ester, thioester, amide, peptide and isopeptide bonds formed by the C-terminal Gly of ubiquitin, a small regulatory protein that can be conjugated to a large range of target proteins. Protein ubiquitination is a post-translational modification of mostly Lys residues that regulates many cellular processes, including protein degradation, intracellular trafficking, cell signaling, autophagy, transcription, translation, and the DNA damage response. OTU1 has been implicated in the ER-associated degradation (ERAD) pathway. In yeast, it counteracts the activity of Ufd2 by deubiquitinating Ufd2 substrates; Ufd2 is a E4 ubiquitin ligase that interacts with Cdc48, an AAA ATPase that plays a central role in the ERAD pathway by chaperoning proteins to the proteasome for destruction. OTU1 also functions as a substrate-processing factor of valosin-containing protein (VCP, the mammalian counterpart of yeast Cdc48) that is required for the retrotranslocation of the ERAD pathway. OTU1 has been shown to preferentially hydrolyze polyubiquitin chains with Lys48 linkages. It contains ubiquitin-like (Ubl) domain with a beta-grasp Ubl fold, a C2H2-type zinc finger, and an OTU (ovarian tumor) domain. This model represents the OTU domain that interacts with ubiquitin and possesses catalytic activity. OTU1 belongs to the OTU family of cysteine proteases that use a conserved cysteine, histidine, and an aspartate, as the catalytic triad. This family also contains plant OTU1 and OTU2.
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