Members of this family adopt a structure consisting of an alpha+beta sandwich with an antiparallel beta-sheet, arranged in a 2(beta-alpha-beta) motif. They are mainly found in mRNA export factors, and mediate the sequence nonspecific nuclear export of cellular mRNAs as well as the sequence-specific export of retroviral mRNAs bearing the constitutive transport element [1].

1: The crystal structure and mutational analysis of a novel RNA-binding domain found in the human Tap nuclear mRNA export factor. Ho DN, Coburn GA, Kang Y, Cullen BR, Georgiadis MM; Proc Natl Acad Sci U S A. 2002;99:1888-1893. PMID:11854490