A Small Molecule That Switches a Ubiquitin Ligase From a Processive to a Distributive Enzymatic Mechanism

  • J Am Chem Soc. 2015 Oct 7;137(39):12442-5. doi: 10.1021/jacs.5b06839.
Stefan G Kathman  1 ,  Ingrid Span  1 ,  Aaron T Smith  1 ,  Ziyang Xu  1 ,  Jennifer Zhan  1 ,  Amy C Rosenzweig  1 ,  Alexander V Statsyuk  1
Affiliations
  • 1. Center for Molecular Innovation and Drug Discovery, Chemistry of Life Processes Institute, Department of Chemistry, Department of Molecular Biosciences, Northwestern University , Silverman Hall, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
PMID: 26371805 DOI: 10.1021/jacs.5b06839
Abstract

E3 Ligases are genetically implicated in many human diseases, yet E3 enzyme mechanisms are not fully understood, and there is a strong need for pharmacological probes of E3s. We report the discovery that the HECT E3 Nedd4-1 is a processive enzyme and that disruption of its processivity by biochemical mutations or small molecules switches Nedd4-1 from a processive to a distributive mechanism of polyubiquitin chain synthesis. Furthermore, we discovered and structurally characterized the first covalent inhibitor of Nedd4-1, which switches Nedd4-1 from a processive to a distributive mechanism. To visualize the binding mode of the Nedd4-1 inhibitor, we used X-ray crystallography and solved the first structure of a Nedd4-1 family Ligase bound to an inhibitor. Importantly, our study shows that processive Nedd4-1, but not the distributive Nedd4-1:inhibitor complex, is able to synthesize polyubiquitin chains on the substrate in the presence of the deubiquitinating enzyme USP8. Therefore, inhibition of E3 Ligase processivity is a viable strategy to design E3 inhibitors. Our study provides fundamental insights into the HECT E3 mechanism and uncovers a novel class of HECT E3 inhibitors.

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