Structural characterization of the PSMA/Glu-490 complex

a Molecular formula of the Glu-490. b A stereo view of the Gluo-490 inhibitor. The Fo-Fc omit map (green) is contoured at 3.0 σ and the inhibitor is shown in stick representation with atoms colored red (oxygen), blue (nitrogen), yellow (sulfur), and cyan (carbon). c Details of interactions between residues of the glutarate sensor (green carbons) and Glu-490 (cyan carbons). CH–π interactions are depicted as dashed lines with distances to the ring centers in Angstroms. The active-site zinc ions are shown as orange spheres. d Surface representation of PSMA with residues of the glutarate sensor interaction with the FMR moiety colored blue, PDB code (7BFZ).

Yiguang Wang, Cyril Bařinka & Xing Yang Research Groups

Significance

Surgery is an efficient way to treat localized prostate cancer (PCa), however, it is challenging to demarcate rapidly and accurately the tumor boundary intraoperatively, as existing tumor detection methods are seldom performed in real-time. To overcome those limitations, we develop a fluorescent molecular rotor that specifically targets the prostate-specific membrane antigen (PSMA), an established marker for PCa. The probes have picomolar affinity (IC₅₀= 63-118 pM) for PSMA and generate virtually instantaneous onset of robust fluorescent signal proportional to the concentration of the PSMA-probe complex. In vitro and ex vivo experiments using PCa cell lines and clinical samples, respectively, indicate the utility of the probe for biomedical applications, including real-time monitoring of endocytosis and tumor staging. Experiments performed in a PCa xenograft model reveal suitability of the probe for imaging applications in vivo.

Zhang, J., … Wang, Y., Bařinka, C. & Yang, X.: A prostate-specific membrane antigen activated molecular rotor for real-time fluorescence imaging,  Nature Comm. (2021)12:5460, https://doi.org/10.1038/s41467-021-25746-6

Overall architecture of the giant E3 ligase HUWE1_N.

a, Domain architecture of HUWE1_N. ARM repeats 1–34 are numbered, with the four insertions indicated. The positions of human HUWE1 insertions, absent in HUWE1_N, are shown in brackets. b, Crystal structure of HUWE1_N. c, Crystal structure of HUWE1_N 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

Significance

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