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Helix-turn-helix



 

In proteins, the helix-turn-helix (HTH) is a major structural motif capable of binding DNA. It is composed of two α helices joined by a short strand of amino acids and is found in many proteins that regulate gene expression.

Its discovery was based on similarities between the genes for Cro, CAP, and λ repressor, which share a common 20-25 amino acid sequence that facilitates DNA recognition. In particular, recognition and binding to DNA is done by the two α helices, one occupying the N-terminal end of the motif, the other at the C-terminus. In most cases, such as in the Cro repressor, the second helix contributes most to DNA recognition, and hence it is often called the "recognition helix". It binds to the major groove of DNA through a series of hydrogen bonds and various 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.

It is also called helix-loop-helix (HLH).

See also

References

  • Brennan R, Matthews B (1989). "The helix-turn-helix DNA binding motif". J. Biol. Chem. 264 (4): 1903-6. PMID 2644244.
  • Matthews B, Ohlendorf D, Anderson W, Takeda Y (1982). "Structure of the DNA-binding region of lac repressor inferred from its homology with cro repressor". Proc. Natl. Acad. Sci. U.S.A. 79 (5): 1428-32. PMID 6951187.


Protein secondary structure
Helices: α-helix | 310 helix | π-helix | β-helix | Polyproline helix | Collagen helix
Extended: β-strand | Turn | Beta hairpin | Beta bulge | α-strand
Supersecondary: Coiled coil | Helix-turn-helix | EF hand
Secondary structure propensities of amino acids
Helix-favoring: Methionine | Alanine | Leucine | Glutamic acid | Glutamine | Lysine
Extended-favoring: Threonine | Isoleucine | Valine | Phenylalanine | Tyrosine | Tryptophan
Disorder-favoring: Glycine | Serine | Proline | Asparagine | Aspartic acid
No preference: Cysteine | Histidine | Arginine
←Primary structure Tertiary structure→
v • d • e
Transcription factors and intracellular receptors
(1) Basic domains
(1.1) Basic leucine zipper (bZIP) Activating transcription factor (1, 2, 3, 4, 5, 6) • AP-1 (c-Fos, FOSB, FOSL1, FOSL2, c-Jun, JUNB, JUND) • BACH (1, 2) • C/EBP (α, β, γ, δ, ε, ζ) • CREB (1, 3) • GABPA • MAF (B, F, G, K) • NRL • NRF1 • XBP1
(1.2) Basic helix-loop-helix (bHLH) ATOH1 • AhR • AHRR • ARNT • ASCL1 • BMAL (ARNTL, ARNTL2) • CLOCK • HIF (1A, 3A) • Myogenic regulatory factors (MyoD, Myogenin, MYF5, MYF6) • NEUROD1 • Twist • USF1
(1.3) bHLH-ZIP Myc • MITF • SREBP (1, 2)
(1.6) Basic helix-span-helix (bHSH) AP-2
(2) Zinc finger
DNA-binding domains
(2.1) Nuclear receptor (Cys4) subfamily 1 (Thyroid hormone (α, β), CAR, FXR, LXR (α, β), PPAR (α, β/δ, γ), PXR, RAR (α, β, γ), ROR (α, β, γ), Rev-ErbA (α, β), VDR) • subfamily 2 (COUP-TF (I, II), Ear-2, HNF4 (α, γ), PNR, RXR (α, β, γ), Testicular receptor (2, 4), TLX) • subfamily 3 (Steroid hormone (Estrogen (α, β), Estrogen related (α, β, γ), Androgen, Glucocorticoid, Mineralocorticoid, Progesterone)) • subfamily 4 NUR (NGFIB, NOR1, NURR1) • subfamily 5 (LRH-1, SF1) • subfamily 6 (GCNF) • subfamily 0 (DAX1, SHP)
(2.2) Other Cys4 GATA (1, 2, 3, 4, 5, 6)
(2.3) Cys2His2 General transcription factors (TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH: 1, 2) • GLI-Krüppel family (1, 2, 3, YY1) • KLF (2, 4, 5, 6, 10, 11, 12, 13) • Sp1 • zinc finger (3, 35, 43, 146, 148, 165, 217, 268, 281, 350) • Zbtb7 (7A) • ZBT (16, 17, 33)
(2.4) Cys6 HIVEP1
(3) Helix-turn-helix
domains
(3.1) Homeo domain ARX • Homeobox (A1, A3, A4, A5, A7, A9, A10, A11, A13, B1, B2, B3, B4, B5, B6, B7, B8, B9, B13, C4, C6, C8, C9, C13, D1, D3, D4, D9, D10, D11, D12, D13) • NANOG • NKX (2-1, 2-5, 3-1) • POU domain (PIT-1, BRN-3: 1, 2, Octamer transcription factor: 1, 2, 3/4, 6, 7)
(3.2) Paired box PAX (1, 2, 3, 4, 5, 6, 7, 8, 9)
(3.3) Fork head / winged helix E2F (1, 2, 3, 4, 5) • FOX proteins (C1, C2, E1, G1, H1, L2, M1, N3, O3, O4, P1, P2, P3)
(3.4) Heat Shock Factors HSF1
(3.5) Tryptophan clusters ELF (4, 5) • Interferon regulatory factors (1, 2, 3, 4, 5, 6, 7, 8) • MYB
(3.6) TEA domain transcriptional enhancer factor 1, 2
(4) β-Scaffold factors with
minor groove contacts
(4.1) Rel homology region NF-κB (NFKB1, NFKB2, REL, RELA, RELB) • NFAT (5, C1, C2, C3, C4)
(4.2) STAT STAT (1, 2, 3, 4, 5, 6)
(4.3) p53 p53
(4.4) MADS box Mef2 (A, B, C, D) • SRF
(4.7) High mobility group HNF (1A, 1B) • LEF1 • SOX (3, 4, 6, 9, 10, 13, 18) • SRY • SSRP1
(4.10) Cold-shock domain CSDA
(4.11) Runt CBF (RUNX1, RUNX2, RUNX3)
(0) Other
transcription factors
(0.2) HMGI(Y) HMGA (1, 2)
(0.3) Pocket domain Rb • RBL1 • RBL2
(0.6) Miscellaneous ARID (1A, 1B, 2, 3A, 3B, 4A) • CAP • Rho/Sigma • R-SMAD
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Helix-turn-helix". A list of authors is available in Wikipedia.
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