<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="PUB00005450"/>]. The human homologue of yeast Rad23A is one example of a nucleotide excision-repair protein that contains both an internal and a C-terminal UBA domain. The solution structure of human Rad23A UBA(2) showed that the domain forms a compact three-helix bundle [<cite idref="PUB00003958"/>]. Comparison of the structures of UBA(1) and UBA(2) reveals that both form very similar folds and have a conserved large hydrophobic surface patch which may be a common protein-interacting surface present in diverse UBA domains. Evidence that ubiquitin binds to UBA domains leads to the prediction that the hydrophobic surface patch of UBA domains interacts with the hydrophobic surface on the five-stranded beta-sheet of ubiquitin [<cite idref="PUB00007089"/>].</p><p>This domain is similar in sequence to the N-terminal domain of translation elongation factor EF1B (or EF-Ts) from bacteria, mitochondria and chloroplasts.</p><p>More information about EF1B (EF-Ts) proteins can be found at Protein of the Month: Elongation Factors [<cite idref="PUB00033962"/>].</p> Ubiquitin-associated/translation elongation factor EF1B, N-terminal