and manganese-regulated repressors show that the DNA binding domain contains three alpha-helices and a pair of antiparallel beta-strands. Helices 2 and 3 comprise the helix-turn-helix motif and the beta-strands are called the wing. [ 3 ] This wHTH topology is similar to the lysR-type HTH. Most dtxR-type metalloregulators bind as dimers