CUEʹd up for Monoubiquitin

The first structures have been obtained for complexes between CUE domains and monoubiquitin, one by NMR (Kang et al., this issue of Cell) and one by X-ray crystallography (Prag et al., this issue of Cell), thus providing insights into ubiquitin recognition by CUE domains. Structural comparisons suggest that different CUE surfaces can interact with ubiquitin, indicating that not all CUE domains are created equal.