Survival Motor Neuron (SMN) protein forms the oligomeric core of a multi-protein complex that functions in spliceosomal snRNP biogenesis. Mutations in the SMN gene cause spinal muscular atrophy (SMA). It has three highly conserved domains: a short N-terminal segment responsible for binding with high affinity to Gemin2, therefore, called Gemin2-binding domain (G2-BD), a central Tudor domain (Pfam:PF06003) that recognises symmetric dimethylarginine (sDMA) modifications in proteins involved in RNA processing, and a C-terminal domain, represented in this entry, referred to as the 'YG-box' [1,2]. This domain contains three overlapping motifs: GxxxGxxxG, YxxxYxxxY and SxxxSxxxSxxxT. The YG-box forms helical oligomers similar to the glycine zippers found in transmembrane channels. The YG-box oligomers are thought to be involved in oligomerization and are likely to be used directly in mediating interactions that are crucial for SMN's functions [1]. It has been reported that nearly half of the known SMA patient missense mutations map to the SMN YG-box [1].

1: The survival motor neuron protein forms soluble glycine zipper oligomers. Martin R, Gupta K, Ninan NS, Perry K, Van Duyne GD; Structure. 2012;20:1929-1939. PMID:23022347

2: Solution structure of the core SMN-Gemin2 complex. Sarachan KL, Valentine KG, Gupta K, Moorman VR, Gledhill JM Jr, Bernens M, Tommos C, Wand AJ, Van Duyne GD; Biochem J. 2012;445:361-370. PMID:22607171