Members of this family, which are predominantly found in prokaryotic 4-alpha-glucanotransferase, adopt a structure composed of six antiparallel beta-strands, four of which form a beta-sheet and another two form a type I' beta-hairpin. The role of this family of domains, has not, as yet, been defined [1].

1: Crystal structure of Thermotoga maritima 4-alpha-glucanotransferase and its acarbose complex: implications for substrate specificity and catalysis. Roujeinikova A, Raasch C, Sedelnikova S, Liebl W, Rice DW; J Mol Biol. 2002;321:149-162. PMID:12139940