This winged helix-turn-helix domain contains an extended C-terminal alpha helix which is responsible for dimerisation of this domain [1].

1: The hyperthermophile protein Sso10a is a dimer of winged helix DNA-binding domains linked by an antiparallel coiled coil rod. Chen L, Chen LR, Zhou XE, Wang Y, Kahsai MA, Clark AT, Edmondson SP, Liu ZJ, Rose JP, Wang BC, Meehan EJ, Shriver JW; J Mol Biol. 2004;341:73-91. PMID:15312764