This family is found towards the C-terminus of the DEAD-box helicases (Pfam:PF00270). In these helicases it is apparently always found in association with Pfam:PF04408. There do seem to be a couple of instances where it occurs by itself - e.g. Swiss:Q84VZ2. The structure PDB:3i4u adopts an OB-fold. helicases (Pfam:PF00270). In these helicases it is apparently always found in association with Pfam:PF04408. This C-terminal domain of the yeast helicase contains an oligonucleotide/oligosaccharide-binding (OB)-fold which seems to be placed at the entrance of the putative nucleic acid cavity. It also constitutes the binding site for the G-patch-containing domain of Pfa1p. When found on DEAH/RHA helicases, this domain is central to the regulation of the helicase activity through its binding of both RNA and G-patch domain proteins [1].

1: Prp43p contains a processive helicase structural architecture with a specific regulatory domain. Walbott H, Mouffok S, Capeyrou R, Lebaron S, Humbert O, van Tilbeurgh H, Henry Y, Leulliot N; EMBO J. 2010;29:2194-2204. PMID:20512115

2: Aspartate-glutamate-alanine-histidine box motif (DEAH)/RNA helicase A helicases sense microbial DNA in human plasmacytoid dendritic cells. Kim T, Pazhoor S, Bao M, Zhang Z, Hanabuchi S, Facchinetti V, Bover L, Plumas J, Chaperot L, Qin J, Liu YJ; Proc Natl Acad Sci U S A. 2010; [Epub ahead of print] PMID:20696886