GO:0043398

Interacting selectively and non-covalently with Helix Loop Helix, a domain of 40-50 residues that occurs in specific DNA-binding proteins that act as transcription factors. The domain is formed of two amphipathic helices joined by a variable length linker region that can form a loop and it mediates protein dimerization. [GOC:go_curators, Prosite:PDOC0038]