Rad23 functions in nucleotide excision repair and proteasome-mediated protein degradation. It has four distinct structural domains that are connected by flexible linker regions, including an N-terminal ubiquitin-like (UBL) domain that binds proteasomes. We report in this NMR study the (1)H, (15)N and (13)C resonance assignments for the backbone and side chain atoms of the Rad23 UBL domain (Rad23(UBL)) with BioMagResBank accession number 25825. We find that a Rad23 proline amino acid (P20) located in a loop undergoes isomerization. The secondary structural elements predicted from the NMR data fit well to that of the Rad23(UBL) when complexed with E4 ubiquitin ligase Ufd2, as reported in a crystallographic structure. These complete assignments can be used to study the protein dynamics of the Rad23(UBL) and its interaction of with other ubiquitin receptors or proteasome subunits.
Keywords: NMR; UV excision repair protein Rad23; Ubiquitin-like domain; Ubiquitin–proteasome pathway.