DNA looping and unlooping by AraC protein

@article{Lobell1990DNALA,
  title={DNA looping and unlooping by AraC protein},
  author={RB Lobell and RF Schleif},
  journal={Science},
  year={1990},
  volume={250},
  pages={528 - 532}
}
Expression of the L-arabinose BAD operon in Escherichia coli is regulated by AraC protein which acts both positively in the presence of arabinose to induce transcription and negatively in the absence of arabinose to repress transcription. The repression of the araBAD promoter is mediated by DNA looping between AraC protein bound at two sites near the promoter separated by 210 base pairs, araI and araO2. In vivo and in vitro experiments presented here show that an AraC dimer, with binding to… 
The role of rigidity in DNA looping-unlooping by AraC.
TLDR
Results are consistent with the light switch mechanism for the action of AraC, refine the model, and extend the range of experimental tests to which it has been subjected.
Apo-AraC actively seeks to loop.
TLDR
These results demonstrate that apo-AraC possesses an intrinsic looping preference that is eliminated by the presence of arabinose, and developed a method for the accurate determination of the relative affinities of AraC for the DNA half-sites araI1, aRAI2, and araO2 and non-specific DNA.
Helical Behavior of the Interdomain Linker of the Escherichia coli AraC Protein.
TLDR
Evidence is provided that, in shifting from the repressing to the inducing state, the behavior of interdomain linker shifts from that of an alpha-helix to that of a flexible nonhelical form, providing a plausible mechanism for arabinose to control the repressed-inducing state of AraC protein.
In vivo induction kinetics of the arabinose promoters in Escherichia coli
TLDR
The induction response of the wild-type arabinose operons from their native chromosomal locations is characterized by primer extension analysis and the relative levels of inducibility in wild- type cells of araBAD, araFGH, and araE are determined to be 6.5, 5, and 1, respectively.
Constitutive Mutations in the Escherichia coli AraC Protein
TLDR
Fluorescence, circular dichroism, and cysteine reactivity measurements show that the constitutive mutations in the core of the dimerization domain lead to a weakening of the support for the arms and reduce the stability of the minus-arabinose arm structure.
Sequence elements in the Escherichia coli araFGH promoter
TLDR
The effects of 11 mutations within the DNA region thought to bind the cyclic AMP receptor protein correlate well with the CRP consensus binding sequence and confirm that this region is responsible for cyclicAMP regulation.
Repression of the araBAD promoter from araO1.
Heterodimers reveal that two arabinose molecules are required for the normal arabinose response of AraC.
TLDR
It is found that the normal arabinose response of AraC requires the binding of twoArabinose molecules, which provides additional constraints on mechanistic models for the action of Ara C.
In Vitro Repression of the gal Promoters by GalR and HU Depends on the Proper Helical Phasing of the Two Operators*
TLDR
It is concluded that the observed in vitro repression of gal transcription in vitro is mediated by DNA looping and the in vitro conditions reflect the in vivo situation.
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References

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TLDR
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TLDR
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TLDR
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  • E. Hamilton, N. Lee
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1988
TLDR
It is suggested that AraC exerts its multiplicity of controls through two alternative states of cooperative interactions with DNA and this model presents the interpretations of activation and repression of the araBAD operon and the autoregulation of theAraC gene.
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TLDR
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TLDR
The locations of DNA binding by the proteins involved with positive and negative regulation of transcription initiation of the L-arabinose operon in Escherichia coli have been determined and suggest the following regulatory mechanism: induction of the araBAD operon occurs when cyclic AMP receptor protein, araC protein, and RNA polymerase are all present and able to bind to DNA.
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TLDR
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TLDR
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