Helix-loop-helix transcription factors

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Helix-loop-helix transcription factors are a structural motif DNA -binding proteins , consisting of a short α- helix is formed by a flexible loop (engl. Loop is) with a second helix longer linked. This HLH motif differs from the helix-turn-helix motif . Due to the flexibility of the loop, one helix can fold back and lie against a second, so that the two monomers can combine to form a four-helix bundle and thus interact with both the DNA and each other.

If an HLH protein lacks an α-helical extension, which is responsible for the interaction with the DNA, then the dimerization of such a torso protein with an intact protein results in inactive HLH heterodimers that lack the ability to stick to a DNA tie. Such torso proteins in excess can block homodimerization of intact HLH proteins and thereby prevent binding to the DNA. Thus, the mechanism of cell heterodimerization provides a control mechanism for inactivating specific gene regulatory proteins .

literature

  • Jeremy M. Berg, John L. Tymoczko, Lubert Stryer : Biochemistry. 6 edition, Spektrum Akademischer Verlag, Heidelberg 2007. ISBN 978-3-8274-1800-5 .
  • Donald Voet, Judith G. Voet: Biochemistry. 3rd edition, John Wiley & Sons, New York 2004. ISBN 0-471-19350-X .
  • Bruce Alberts , Alexander Johnson, Peter Walter, Julian Lewis, Martin Raff, Keith Roberts: Molecular Biology of the Cell , 5th Edition, Taylor & Francis 2007, ISBN 978-0815341062 .