A structural element within the HUWE1 HECT domain modulates self-ubiquitination and substrate ubiquitination activities.
Publication Type:Journal Article
Source:J Biol Chem, Volume 285, Issue 8, p.5664-73 (2010)
Keywords:Catalytic Domain, Crystallography, X-Ray, Humans, Myeloid Cell Leukemia Sequence 1 Protein, Protein Structure, Secondary, Proto-Oncogene Proteins c-bcl-2, Substrate Specificity, Ubiquitin, Ubiquitin-Protein Ligases, Ubiquitination
<p>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.</p>