科研之友
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摘要
Ubiquitin-like modifications are important mechanisms in cellular regulation, and are carried out through several steps with reaction intermediates being thioester conjugates of ubiquitin-like proteins with El, E2, and sometimes E3. Despite their importance, a thorough characterization of the intrinsic stability of these thioester intermediates has been lacking. In this study, we investigated the intrinsic stability by using a model compound and the Ubc9 similar to SUMO-1 thioester conjugate. The Ubc9 similar to SUMO-1 thioester intermediate has a half life of approximately 3.6 h (hydrolysis rate k = 5.33 /- 2.8 x 10(-5) s(-1)), and the stability decreased slightly under denaturing conditions (k = 12.5 /- 1.8 x 10(-5) s(-1)), indicating a moderate effect of the three-dimensional structural context on the stability of these intermediates. Binding to active and inactive E3, (RanBP2) also has only a moderate effect on the hydrolysis rate (13.8 /- 0.8 x 10(-5) s(-1) for active E3 versus 7.38 /- 0.7 x 10(-5) s(-1) for inactive E3). The intrinsically high stability of these intermediates suggests that unwanted thioester intermediates may be eliminated enzymatically, such as by thioesterases, to regulate their intracellular abundance and trafficking in the control of ubiquitin-like modifications.
- 出版日期2009-12
