This family is an unusual, usually C-terminal, RNA-recognition motif found in fungi. In yeast it is the fourth RRM domain on the essential splicing factor Prp24. Structurally, it has a non-canonical RRM fold with the expected beta-aloha-beta-beta-alpha-beta RRM-fold is flanked by N- and C-terminal alpha-helices. These two additional flanking alpha-helices occlude the beta-sheet face. The electropositive surface thereby presented is an alternative RNA-binding surface that allows both binding and unwinding of the U6 small nuclear RNA's internal stem loop, at least in vitro [1].

1: A novel occluded RNA recognition motif in Prp24 unwinds the U6 RNA internal stem loop. Martin-Tumasz S, Richie AC, Clos LJ 2nd, Brow DA, Butcher SE; Nucleic Acids Res. 2011;39:7837-7847. PMID:21653550