Helix-Loop-Helix Domain

Cancer Terms -> Anatomic Structure System or Substance -> Microanatomy -> Macromolecular Structure -> Protein Structure -> Protein Domain -> Ligand Binding Domain -> DNA Binding Domain -> Helix-Loop-Helix Domain

Helix-Loop-Helix Domain Definition

In transcription regulators of cell cycle control, cell determination, and cell differentiation, the conserved HLH (Helix-Loop-Helix) Domain of 40-50 amino acids forms amphipathic helixes between a variable loop. HLHs typically mediate homo- or heterodimerization through interactions with self or other motifs to activate or inactivate trans-activating function. The N-helix often contains DNA-interacting basic residues; the C-helix typically contains characteristically spaced hydrophobic residues. An adjacent basic region of 15 amino acids in most HLH proteins binds to DNA. Basic (b)HLH proteins bind variants of the 'CANNTG' E-box. Proteins lacking the basic domain act as inhibitors, failing to bind DNA. bHLH proteins exhibit specific dimerization partner combinations. In calcium-binding proteins, certain invariant hydrophilic loop residues in the HLH motif bind calcium. (NCI)

Helix-Loop-Helix Domain Synonyms

Helix-Loop-Helix Domain, HLH Domain, HLH Motif, Helix-Loop-Helix Motif

Terms in Helix-Loop-Helix Domain category

bHLH-Zip Domain
bHLH Domain