title: A structural element within the HUWE1 HECT domain modulates self-ubiquitination and substrate ubiquitination activities.
abstract: E3 ubiquitin ligases catalyze the final step of ubiquitin conjugation and regulate numerous cellular processes. The HECT class of E3 ubiquitin (Ub) ligases directly transfers Ub from bound E2 enzyme to a myriad of substrates. The catalytic domain of HECT Ub ligases has a bilobal architecture that separates the E2 binding region and catalytic site. An important question regarding HECT domain function is the control of ligase activity and specificity. Here we present a functional analysis of the HECT domain of the E3 ligase HUWE1 based on crystal structures and show that a single N-terminal helix significantly stabilizes the HECT domain. We observe that this element modulates HECT domain activity, as measured by self-ubiquitination induced in the absence of this helix, as distinct from its effects on Ub conjugation of substrate Mcl-1. Such subtle changes to the protein may be at the heart of the vast spectrum of substrate specificities displayed by HECT domain E3 ligases.
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA.
authors.forename: Renuka K
authors.initials: RK
authors.lastname: Pandya
authors.forename: James R
authors.initials: JR
authors.lastname: Partridge
authors.forename: Kerry Routenberg
authors.initials: KR
authors.lastname: Love
authors.forename: Thomas U
authors.initials: TU
authors.lastname: Schwartz
authors.forename: Hidde L
authors.initials: HL
authors.lastname: Ploegh
mesh_terms: D020134:Catalytic Domain / Q000502:physiology; D018360:Crystallography, X-Ray; D006801:Humans; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D017433:Protein Structure, Secondary / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity / Q000502:physiology; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination / Q000502:physiology*
chemical_list: D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; C502830:HUWE1 protein, human; D044767:Ubiquitin-Protein Ligases