Helix-turn-helix

The λ repressor of bacteriophage lambda employs two helix-turn-helix motifs (left; green) to bind DNA (right; blue and red). The λ repressor protein in this image is a dimer.
Helix-turn-helix
Identifiers
SymbolHTH
Pfam clanCL0123
ECOD101.1

Helix-turn-helix is a DNA-binding domain (DBD). The helix-turn-helix (HTH) is a major structural motif capable of binding DNA. Each monomer incorporates two α helices, joined by a short strand of amino acids, that bind to the major groove of DNA. The HTH motif occurs in many proteins that regulate gene expression. It should not be confused with the helix–loop–helix motif.[1]

  1. ^ Brennan RG, Matthews BW (February 1989). "The helix-turn-helix DNA binding motif". The Journal of Biological Chemistry. 264 (4): 1903–6. doi:10.1016/S0021-9258(18)94115-3. PMID 2644244.