Helix-turn-helix

Source: Wikipedia, the free encyclopedia.
bacteriophage lambda employs two helix-turn-helix motifs (left; green) to bind DNA (right; blue and red). The λ repressor protein in this image is a dimer
.

Helix-turn-helix is a

helix–loop–helix motif.[1]

Discovery

The discovery of the helix-turn-helix motif was based on similarities between several genes encoding

λ repressor, which were found to share a common 20–25 amino acid sequence that facilitates DNA recognition.[2][3][4][5]

Function

The helix-turn-helix motif is a DNA-binding motif. The recognition and binding to DNA by helix-turn-helix proteins is done by the two α helices, one occupying the

Van der Waals interactions with exposed bases. The other α helix stabilizes the interaction between protein and DNA, but does not play a particularly strong role in its recognition.[2] The recognition helix and its preceding helix always have the same relative orientation.[6]

Classification of helix-turn-helix motifs

Several attempts have been made to classify the helix-turn-helix motifs based on their structure and the spatial arrangement of their helices.[6][7][8] Some of the main types are described below.

Di-helical

The di-helical helix-turn-helix motif is the simplest helix-turn-helix motif. A fragment of Engrailed homeodomain encompassing only the two helices and the turn was found to be an ultrafast independently folding protein domain.[9]

Tri-helical

An example of this motif is found in the transcriptional activator Myb.[10]

Tetra-helical

The tetra-helical helix-turn-helix motif has an additional

bacterial transcription factors and the helix-turn-helix motif found in the TetR repressors.[11] Multihelical versions with additional helices also occur.[12]

Winged helix-turn-helix

The winged helix-turn-helix (wHTH) motif is formed by a 3-helical bundle and a 3- or 4-strand

beta-sheet scaffold arranged in the order α1-β1-β2-α2-α3-β3-β4 where the third helix is the DNA recognition helix.[13][14]

Other modified helix-turn-helix motifs

Other derivatives of the helix-turn-helix motif include the DNA-binding domain found in

multiple antibiotic resistance, which forms a winged helix-turn-helix with an additional C-terminal alpha helix.[8][15]

See also

References

  1. PMID 2644244
    .
  2. ^
    PMID 6951187
    .
  3. S2CID 4360799
    .
  4. S2CID 568056
    .
  5. S2CID 39169630
    .
  6. ^
    PMID 8831795
    .
  7. S2CID 3037519
    .
  8. ^
    PMID 15808743
    .
  9. PMID 17517666
    .
  10. PMID 1631139
    .
  11. PMID 8153629
    .
  12. PMID 10545119
    .
  13. PMID 8598195
    .
  14. PMID 9570133
    .
  15. S2CID 19608515
    .

Further reading

External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Helix-turn-helix&oldid=1219063613"