helix-loop-helix

noun

A structural motif where two alpha helices are connected by a highly flexible amino acid loop, allowing the helices to pack together. Usually requires forming a dimer with another HLH protein before binding DNA.

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Meanings

nounhelix-loop-helix (plural helix-loop-helices, abbreviation HLH)

plural helix-loop-helices · abbreviation HLH

  1. biochemistryA structural motif where two alpha helices are connected by a highly flexible amino acid loop, allowing the helices to pack together. Usually requires forming a dimer with another HLH protein before binding DNA.

Origin

From helix + loop + helix. The term got its name from its distinct physical geometry; two alpha helices separated and connected by a flexible chain of amino acids known as a "loop", allowing the helices to pack together tightly.

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Cite this entry
APA

helix-loop-helix. (n.d.). In WatkinsX Dictionary. Retrieved November 4, 2026, from https://dictionary.watkinsx.com/word/helix-loop-helix

MLA

“helix-loop-helix.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/helix-loop-helix. Accessed November 4, 2026.

Chicago

WatkinsX Dictionary, s.v. “helix-loop-helix,” accessed November 4, 2026, https://dictionary.watkinsx.com/word/helix-loop-helix.

Source: helix-loop-helix on Wiktionary, CC BY-SA 4.0.