Members of this family adopt a secondary structure consisting of a four-stranded beta sheet and one alpha helix. They are predominantly RNA-binding domains, mostly found in Pseudouridine synthase II TruB [1].

1: Cocrystal structure of a tRNA Psi55 pseudouridine synthase: nucleotide flipping by an RNA-modifying enzyme. Hoang C, Ferre-D'Amare AR; Cell. 2001;107:929-939. PMID:11779468