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Synthesis and characterization of fluorescent ubiquitin derivatives as highly sensitive substrates for the deubiquitinating enzymes UCH-L3 and USP-2.

Tirat-Boeuf, Aline and Schilb, Alain and Riou, Virginie and Leder, Lukas and Gerhartz, Bernd and Zimmermann, Johann and Worpenberg-Pietruk, Susanne and Eidhoff, Ulf and Freuler, Felix and Stettler, Thomas and Mayr, Lorenz and Ottl, Johannes and Leuenberger, Beate and Filipuzzi, Ireos (2005) Synthesis and characterization of fluorescent ubiquitin derivatives as highly sensitive substrates for the deubiquitinating enzymes UCH-L3 and USP-2. Analytical Biochemistry, 343 (2). pp. 244-255. ISSN 0003-2697

Abstract

Deubiquitinating enzymes (DUBs) catalyze the removal of attached ubiquitin molecules from amino groups of target proteins. The large family of DUBs plays an important role in the regulation of the intracellular homeostasis of different proteins and influences therefore key events such as cell division, apoptosis, etc. The DUB family members UCH-L3 and USP2 are believed to inhibit the degradation of various tumor-growth-promoting proteins by removing the trigger for degradation. Inhibitors of these enzymes should therefore lead to enhanced degradation of oncoproteins and may thus stop tumor growth. To develop an enzymatic assay for the search of UCH-L3 and USP2 inhibitors, C-terminally labeled ubiquitin substrates were enzymatically synthesized. We have used the ubiquitin-activating enzyme E1 and one of the ubiquitin-conjugating enzymes E2 to attach a fluorescent lysine derivative to the C terminus of ubiquitin. Since only the epsilon-NH(2) group of the lysine derivatives was free and reactive, the conjugates closely mimic the isopeptide bond between the ubiquitin and the lysine side chains of the targeted proteins. Various substrates were synthesized by this approach and characterized enzymatically with the two DUBs. The variant consisting of the fusion protein between the large N-terminal NusA tag and the ubiquitin which was modified with alpha-NH(2)-tetramethylrhodamin-lysine, was found to give the highest dynamic range in a fluorescence polarization readout. Therefore we have chosen this substrate for the development of a miniaturized, fluorescence-polarization-based high-throughput screening assay.

Item Type: Article
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Additional Information: author can archive post-print (ie final draft post-refereeing); Publisher's version/PDF cannot be used
Keywords: Ubiquitin pathway; UCH-L3; USP-2; Cancer
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Date Deposited: 14 Dec 2009 13:57
Last Modified: 31 Jan 2013 01:12
URI: https://oak.novartis.com/id/eprint/596

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