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Protein Motifs: the Helix-Loop-Helix Motif

  1. Fred Sablitzky

Published Online: 3 MAY 2005

DOI: 10.1038/npg.els.0002713



How to Cite

Sablitzky, F. 2005. Protein Motifs: the Helix-Loop-Helix Motif. eLS. .

Author Information

  1. The University of Nottingham, Institute of Genetics, Nottingham, UK

Publication History

  1. Published Online: 3 MAY 2005


The helix-loop-helix (HLH) domain is characterized by two sets of amino acid sequences that fold into amphipathic α helices separated by a flexible linker or ‘loop’ of variable amino acid sequence and length. The HLH domain is a dimerization domain that allows proteins to form homo- and/or heterodimers.


  • homo- and heterodimers;
  • basic DNA-binding domain;
  • e box;
  • leucine zipper;
  • PAS domain