This family is the homodimerisation domain of quaking proteins. Quaking-dimer is a helix-turn-helix dimer with an additional helix in the turn region. Dimerisation is required for adequate RNA-binding. Quaking is a prototypical member of the STAR (signal transducer and activator of RNA) protein family, which plays key roles in post-transcriptional gene regulation by controlling mRNA translation, stability and splicing [1]. STAR_dimer is the homodimerisation domain, Qua1 of the STAR domain of a series of proteins referred to as STAR/GSG, or Signal Transduction and Activation of RNA/GRP33, Sam68, GLD-1 family. These are conserved in higher eukaryotes and are RNA-binding transcriptional regulators. The STAR domain is a KH domain flanked by two homologous regions, Qua1 and Qua2. Qua1, this family, is the homodimerisation domain, and the KH plus Qua2 is the RNA-binding region [2].

1: Structural analysis of the quaking homodimerization interface. Beuck C, Qu S, Fagg WS, Ares M Jr, Williamson JR; J Mol Biol. 2012;423:766-781. PMID:22982292

2: Structure of the GLD-1 homodimerization domain: insights into STAR protein-mediated translational regulation. Beuck C, Szymczyna BR, Kerkow DE, Carmel AB, Columbus L, Stanfield RL, Williamson JR; Structure. 2010;18:377-389. PMID:20223220