Domain is found in an undescribed set of proteins [1]. Normally occurs uniquely within a sequence, but is found as a tandem repeat (Swiss:Q9X8B8). Shows interesting phylogenetic distribution with majority of examples in bacteria and archaea, but it is also found in some fungal proteins. The hypothetical protein TT1751 from Thermus thermophilus has a beta-alpha-beta(4)-alpha structural fold [2].

1: New Knowledge from Old: In silico discovery of novel protein domains in Streptomyces coelicolor. Yeats C, Bentley S, Bateman A; BMC Microbiol 2003;3:3-3. PMID:12625841

2: Crystal structure of a conserved hypothetical protein TT1751 from Thermus thermophilus HB8. Kishishita S, Tatsuguchi A, Ushikoshi-Nakayama R, Terada T, Kuramitsu S, Park SY, Tame JR, Shirouzu M, Yokoyama S; Proteins. 2004;57:883-887. PMID:15481054