α1-β1-β2-α2-α3-β3-β4 where the third helix is the DNA recognition helix. Other modified helix-turn-helix motifs Other derivatives of the helix-turn-helix motif include the DNA-binding domain found in MarR, a regulator of multiple antibiotic resistance, which forms a winged helix-turn-helix with an additional C-terminal alpha helix. See also DNA-binding domain DNA-binding protein Secondary structure Zinc finger References Further reading External links Helix-turn-helix motif, lambda-like repressor, from EMBL Full PDB entry for PDB ID 1LMB Cro/C1-type HTH domain, more HTHs in PROSITE Protein structural motifs Transcription factors DNA-binding substances Protein domains