This small domain is composed of three alpha helices. This family includes the previously defined UBA and TS-N domains. The UBA-domain (ubiquitin associated domain) is a novel sequence motif found in several proteins having connections to ubiquitin and the ubiquitination pathway. The structure of the UBA domain consists of a compact three helix bundle [1]. This domain is found at the N terminus of EF-TS hence the name TS-N. The structure of EF-TS is known and this domain is implicated in its interaction with EF-TU [2]. The domain has been found in non EF-TS proteins such as alpha-NAC Swiss:P70670 and MJ0280 Swiss:Q57728 [1].

1: Structure of a human DNA repair protein UBA domain that interacts with HIV-1 Vpr. Dieckmann T, Withers-Ward ES, Jarosinski MA, Liu CF, Chen IS, Feigon J; Nat Struct Biol 1998;5:1042-1047. PMID:9846873

2: Comparative genomics of the Archaea (Euryarchaeota): evolution of conserved protein families, the stable core, and the variable shell. Makarova KS, Aravind L, Galperin MY, Grishin NV, Tatusov RL, Wolf YI, Koonin EV; Genome Res 1999;9:608-628. PMID:10413400

3: The structure of the Escherichia coli EF-Tu.EF-Ts complex at 2.5 A resolution. Kawashima T, Berthet-Colominas C, Wulff M, Cusack S, Leberman R; Nature 1996;379:511-518. PMID:8596629