Overall architecture of the giant E3 ligase HUWE1N.
a, Domain architecture of HUWE1N. ARM repeats 1–34 are numbered, with the four insertions indicated. The positions of human HUWE1 insertions, absent in HUWE1N, are shown in brackets. b, Crystal structure of HUWE1N. c, Crystal structure of HUWE1N shown in cartoon representation from four different views, using the same color coding as in a (catalytic Cys in red). A schematic cartoon illustrates the snake-like organization of the E3 ligase. d, Negative-stain EM analysis of CeHUWE1. The obtained EM density is shown from two viewpoints, with approximate dimensions indicated. e, Organization and increasing complexity of HUWE1.
Tim Clausen Research Group
HUWE1 is a universal quality-control E3 ligase that marks diverse client proteins for proteasomal degradation. Although the giant HECT enzyme is an essential component of the ubiquitin–proteasome system closely linked with severe human diseases, its molecular mechanism is little understood. Here, we present the crystal structure of NematocidaHUWE1, revealing how a single E3 enzyme has specificity for a multitude of unrelated substrates. The protein adopts a remarkable snake-like structure, where the C-terminal HECT domain heads an extended alpha-solenoid body that coils in on itself and houses various protein–protein interaction modules. Our integrative structural analysis shows that this ring structure is highly dynamic, enabling the flexible HECT domain to reach protein targets presented by the various acceptor sites. Together, our data demonstrate how HUWE1 is regulated by its unique structure, adapting a promiscuous E3 ligase to selectively target unassembled orphan proteins.
Grabarczyk, D.B., Petrova,O.A., Deszcz, L., Kurzbauer, R., Murphy, P., Ahel, J., Vogel, A., Gogova, R., Faas, V., Kordic, D., Schleiffer, A., Meinhart, A:, Imre, R., Lehner, A., Neuhold, J., Bader, G., Stolt-Bergner, P., Böttcher, J., Wolkerstorfer, B., Fischer, G., Grishkovskaya, I., Haselbach, D., Kessler,D., and Clausen T.: HUWE1 employs a giant substrate-binding ring to feed and regulate its HECT E3 domain, Nat. Chem. Biol. (2021) https://doi.org/10.1038/s41589-021-00831-5