English
helix-loop-helix
From helix + loop + helix.
A compound of helix + loop + helix
Proto-Indo-European *klewb- ‘to spring’
Proto-Germanic *hlaupaną ‘to leap, run’
Old Norse hlaupa ‘to leap’
Old Norse hlaup ‘a run’
Middle English loupe ‘noose, loop’
English loop
The story
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.
Today it means
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.
Language periods are conventional ranges, not dates for this word.
Etymograph / helix-loop-helix