Source:http://linkedlifedata.com/resource/umls/id/C0206678
MSH: Recurring supersecondary structures characterized by 20 amino acids folding into two alpha helices connected by a non-helical "loop" segment. They are found in many sequence-specific DNA-BINDING PROTEINS and in CALCIUM-BINDING PROTEINS.,NCI: 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