This domain, approximately 40 residues in length, is mainly found in KH-domain containing, RNA-binding, signal transduction-associated protein 1 from yeast to human [1]. It forms a homodimer composed of a perpendicular interaction of two helical hairpins, and the Qua1 domain is sufficient for homodimerization which is required for the regulation of alternative splicing [2].

1: STAR, a gene family involved in signal transduction and activation of RNA. Vernet C and Artzt K. Trends Genet. 13(12), 479-484 (1997). PMID:9433137

2: Structural basis for homodimerization of the Src-associated during mitosis, 68-kDa protein (Sam68) Qua1 domain. Meyer NH, Tripsianes K, Vincendeau M, Madl T, Kateb F, Brack-Werner R, Sattler M. J Biol Chem. 285(37):28893-901 (2010). PMID:20610388