Members of this family of DNA-binding domains are predominantly found in the prokaryotic transcriptional regulator MerR. They adopt a structure consisting of a core of three alpha helices, with an architecture that is similar to that of the 'winged helix' fold [1].

1: Molecular basis of metal-ion selectivity and zeptomolar sensitivity by CueR. Changela A, Chen K, Xue Y, Holschen J, Outten CE, O'Halloran TV, Mondragon A; Science. 2003;301:1383-1387. PMID:12958362