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Updated: Aug 9, 2026

Functional Characterization of RING-Type E3 Ubiquitin Ligases In Vitro and In Planta
Published on: December 5, 2019
The RING domain of mitochondrial E3 ubiquitin ligase 1 and its complex with Ube2D2: crystallization and X-ray
Sang Ok Lee1, Chong Kil Lee2, Kyoung Seok Ryu3
1Disease Target Structure Research Center, Division of Biomedical Research, KRIBB, Daejeon 34141, Republic of Korea.
Abstract:
Mitochondrial E3 ubiquitin ligase 1 (MUL1) is located in the mitochondrial outer membrane and regulates various biological processes, including apoptosis, cell growth, mitophagy and mitochondrial dynamics. The C-terminal region of MUL1 faces the cytoplasm and contains the RING domain (MUL1-RING) where the Ub~E2 thioester binds. Unlike most RING-type E3 enzymes, MUL1-RING alone does not have an additional region that recruits a substrate protein, yet is still able to ubiquitylate the substrate, the p53 protein. Nevertheless, the exact mechanism of the ubiquitylation of p53 by MUL1-RING has not yet been elucidated. In order to understand this novel ubiquitylation mechanism, it is necessary to determine the three-dimensional structures of MUL1-RING and of its complex with the cognate E2 enzyme. Here, Ube2D2 was validated as a functional E2 enzyme for the ubiquitylation of the p53 transactivation domain (p53-TAD) by MUL1-RING, and purification and crystallization processes for MUL1-RING and the MUL1-RING-Ube2D2 complex are reported.
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