Structural basis for Ufm1 recognition by UfSP.

Ubiquitin and ubiquitin-like proteins (Ubls) are involved in a variety of cellular functions, and dysfunction of these proteins often leads to disease, thus requiring the precise molecular recognition of the partner. Here, we report a structural basis for the recognition of Ufm1 by the Ufm1-specific protease (UfSP), both from Caenorhabditis elegans. Ufm1 functions in endoplasmic reticulum homeostasis, cell cycle regulation, and dysfunctions of this protein can result in breast cancer and neurological disorders. The structure reveals that in addition to the extended β-structure at the C-terminus of cUfm1, the interactions made by the completely conserved residues in Ufm1 orthologs, Pro88-Val92, corresponding to P6-P2 positions from the cleavage site, seem to be important for the specific recognition of Ufm1 by cUfSP.