G3DSA:4.10.280.10

Helix-loop-helix DNA-binding domain

CATH-Gene3D entry
Member databaseCATH-Gene3D
CATH-Gene3D typehomologous superfamily

Description
Imported from IPR036638

This domain is found in a number of eukaryotic proteins, which probably are sequence specific DNA-binding proteins that act as transcription factors, share a conserved domain of 40 to 50 amino acid residues. It has been proposed
[2]
that this domain is formed of two amphipathic helices joined by a variable length linker region that could form a loop. This 'helix-loop-helix' (HLH) domain mediates protein dimerisation and has been found in the proteins listed below
[1]
. Most of these proteins have an extra basic region of about 15 amino acid residues that is adjacent to the HLH domain and specifically binds to DNA. They are referred as basic helix-loop-helix proteins (bHLH), and are classified in two groups: class A (ubiquitous) and class B (tissue-specific). Members of the bHLH family bind variations on the core sequence 'CANNTG', also referred to as the E-box motif. The homo- or heterodimerisation mediated by the HLH domain is independent of, but necessary for DNA binding, as two basic regions are required for DNA binding activity. The HLH proteins lacking the basic domain (Emc, Id) function as negative regulators, since they form heterodimers, but fail to bind DNA. The hairy-related proteins (hairy, E(spl), deadpan) also repress transcription although they can bind DNA. The proteins of this subfamily act together with co-repressor proteins, like groucho, through their -terminal motif WRPW.

References
Imported from IPR036638

1.Function of the c-Myc oncoprotein. Kato GJ, Dang CV. FASEB J. 6, 3065-72, (1992). View articlePMID: 1521738

2.A new DNA binding and dimerization motif in immunoglobulin enhancer binding, daughterless, MyoD, and myc proteins. Murre C, McCaw PS, Baltimore D. Cell 56, 777-83, (1989). View articlePMID: 2493990

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