-  Helix-turn-helix domains
-  Superclass
-  "TRANSFAC class description C0035: The helix-turn-helix superclass is a particularly large and heterogeneous family of transcription factors. Their DNA-binding motif appeared very early during evolution since it is found in prokaryotic and bacteriophage regulators as well as in mammalian transcriptional activators and repressors (PMID 6236744, PMID 6330566, PMID 6429549). Presumably due to this property, most of them fulfill elementary functions in eukaryotes such as developmental regulation and determination of differentiation processes. In general, they comprise a DNA-recognition helix which inserts into the major DNA groove, another one which exerts unspecific stabilizing backbone interactions, and in most cases additional helices which help to stabilize the overall structure of the DNA-binding module."