helix loop helix domain;

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                   ....*....|....*....|....*....|....*....|....*...
gi 57242784     32 NRRAHLRLCLERLKVLIPLGPDCTRHTTLGLLNKAKAHIKKLEEAERK 79
Cdd:smart00353   6 RRRRKINEAFDELRSLLPTLPKNKKLSKAEILRLAIEYIKSLQEELQK 53

basic Helix-Loop-Helix-zipper (bHLHzip) domain found in the Mad family; Members of the Mad family (Mad1, Mxi, Mad3, and Mad4) bear the bHLHzip domain (also known as basic-helix-loop-helix-leucine-zipper or bHLH-LZ domain), which mediates heterodimerization to Max and the sequence-specific DNA binding ability to E-box DNA. Mad family proteins can repress transcription at the E-box through their interaction with co-repressors. Mad family proteins antagonize Myc function in transactivation and transformation and they are growth/tumor suppressors. The developmental phenotypes of the individual Mad family member knockout mice are relatively mild- all these mice have been shown to be viable and normal.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 57242784  32 NRRAHLRLCLERLKVLIPLGPDCTRHTTLGLLNKAKAHIKKLEEAERKSQHQLENLEREQRFLKWRL 98
Cdd:cd11401  10 NRRAHLRLCLERLKELVPLGPDATRHTTLSLLTKAKAYIKNLEDKEKRQRQQKEQLRREQRELKRRL 76

basic Helix-Loop-Helix-zipper (bHLHzip) domain found in Max-associated protein 4 (Mad4) and similar proteins; Mad4, also termed Max dimerization protein 4, or Max dimerizer 4 (MXD4), or Class C basic helix-loop-helix protein 12 (bHLHc12), or Max-interacting transcriptional repressor MAD4, is a bHLHZip Max-interacting transcriptional repressor that suppresses c-myc dependent transformation and is expressed during neural and epidermal differentiation. It is regulated by a transcriptional repressor complex that contains Miz-1 and c-Myc.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 57242784  25 SSNTSTANRRAHLRLCLERLKVLIPLGPDCTRHTTLGLLNKAKAHIKKLEEAERKSQHQLENLEREQRFLKWRLEQLQgP 104
Cdd:cd18929   5 SHNELEKHRRAKLRLYLEQLKQLVPLGPDSTRHTTLSLLKRAKMHIKKLEEQDRKALNIKEQLQREHRYLKRRLEQLS-V 83

                ....*
gi 57242784 105 QEMER 109
Cdd:cd18929  84 QGMER 88

basic Helix-Loop-Helix-zipper (bHLHzip) domain found in Max-binding protein Mnt and similar proteins; Mnt, also termed Class D basic helix-loop-helix protein 3 (bHLHd3), or Myc antagonist MNT, or protein ROX, is a bHLHZip transcriptional repressor that binds DNA as a heterodimer with MAX. It binds to the canonical E box sequence 5'-CACGTG-3' and, with higher affinity, to 5'-CACGCG-3'. Mnt has an important role as an antagonist and regulator of Myc activities and it is a potential tumor suppressor. Mnt is ubiquitously expressed. Mnt-deficient mice shown to exhibit early postnatal lethality.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 57242784  32 NRRAHLRLCLERLKVLIPLGPDcTRHTTLGLLNKAKAHIKKLEEAERKSQHQLENLEREQRFLKWRL 98
Cdd:cd11402  12 NRRAHLKECFETLKRQIPNLDD-KKTSNLNILRSALRYIQILKRKEKEYEHEMERLAREKIALQQRL 77

basic Helix-Loop-Helix-zipper (bHLHzip) domain found in the Myc family; The Myc family is a member of the bHLHzip family of transcription factors that play important roles in the control of normal cell proliferation, growth, survival and differentiation. All Myc isoforms contain two independently functioning polypeptide chain regions: N-terminal transactivating residues and a C-terminal bHLHzip segment. The bHLHzip family of bHLH transcription factors are characterized by a highly conserved N-terminal basic region that may bind DNA at a consensus hexanucleotide sequence known as the E-box (CANNTG) followed by HLH and leucine zipper motifs that may interact with other proteins to form homo- and heterodimers. Myc heterodimerizes with Max enabling specific binding to E-box DNA sequences in the promoters of target genes. The Myc proto-oncoprotein family includes at least five different functional members: c-, N-, L-, S- and B-Myc (which is lacking the bHLH domain).

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 57242784  33 RRAHLRLCLERLKVLIPLGPDCTRHTTLGLLNKAKAHIKKLEEAERKSQHQLENLEREQRFLKWRLEQL 101
Cdd:cd11400  12 RRNDLKNSFEKLRDLVPELADNEKASKVVILKKATEYIKQLQQEEKKLEKEKDKLKARNEQLRKKLERL 80

basic Helix Loop Helix (bHLH) domain superfamily; bHLH proteins are transcriptional regulators that are found in organisms from yeast to humans. Members of the bHLH superfamily have two highly conserved and functionally distinct regions. The basic part is at the amino end of the bHLH that may bind DNA to a consensus hexanucleotide sequence known as the E box (CANNTG). Different families of bHLH proteins recognize different E-box consensus sequences. At the carboxyl-terminal end of the region is the HLH region that interacts with other proteins to form homo- and heterodimers. bHLH proteins function as a diverse set of regulatory factors because they recognize different DNA sequences and dimerize with different proteins. The bHLH proteins can be divided to cell-type specific and widely expressed proteins. The cell-type specific members of bHLH superfamily are involved in cell-fate determination and act in neurogenesis, cardiogenesis, myogenesis, and hematopoiesis.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....
gi 57242784  32 NRRAHLRLCLERLKVLIPLGPDCTRHTTLGLLNKAKAHIKKLEE 75
Cdd:cd00083   3 RRRDKINDAFEELKRLLPELPDSKKLSKASILQKAVEYIRELQS 46