<p>UBA domains are a commonly occurring sequence motif of approximately 45 amino acid residues that are found in diverse proteins involved in the ubiquitin/proteasome pathway, DNA excision-repair, and cell signalling via protein kinases [<cite idref="PUB00007089"/>]. HHR23A, the human homologue of yeast Rad23A is a nucleotide excision-repair protein that contains both an internal and a C-terminal UBA domain. The fold of the UBA domain consists of a compact three-helical bundle with a right-handed twist, and have a conserved hydrophobic surface patch for protein-protein interactions. UBA-like domains can be found in other proteins as well, such as the TS-N domain in the elongation factor Ts (EF-Ts), which catalyses the recycling of the GTPase EF-Tu required for the binding of aminoacyl-tRNA top the ribosomal A site [<cite idref="PUB00013202"/>]; and the C-terminal domain of TAP/NXF1, which functions in nuclear export through the interaction of its UBA-like domain with FG nucleoporins [<cite idref="PUB00013203"/>].</p> UBA-like