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Regulatory mechanism of the light-activable allosteric switch LOV–TAP for the control of DNA binding: A computer simulation study

Authors

  • Emanuel Peter,

    1. Department of Chemistry and Pharmacy, Institute of Physical and Theoretical Chemistry, University of Regensburg, Regensburg D-93040, Germany
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  • Bernhard Dick,

    1. Department of Chemistry and Pharmacy, Institute of Physical and Theoretical Chemistry, University of Regensburg, Regensburg D-93040, Germany
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  • Stephan A. Baeurle

    Corresponding author
    1. Department of Chemistry and Pharmacy, Institute of Physical and Theoretical Chemistry, University of Regensburg, Regensburg D-93040, Germany
    • Department of Chemistry and Pharmacy, Institute of Physical and Theoretical Chemistry, University of Regensburg, Regensburg D-93040, Germany
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Abstract

The spatio-temporal control of gene expression is fundamental to elucidate cell proliferation and deregulation phenomena in living systems. Novel approaches based on light-sensitive multiprotein complexes have recently been devised, showing promising perspectives for the noninvasive and reversible modulation of the DNA-transcriptional activity in vivo. This has lately been demonstrated in a striking way through the generation of the artificial protein construct light-oxygen-voltage (LOV)–tryptophan-activated protein (TAP), in which the LOV-2-Jα photoswitch of phototropin1 from Avena sativa (AsLOV2-Jα) has been ligated to the tryptophan-repressor (TrpR) protein from Escherichia coli. Although tremendous progress has been achieved on the generation of such protein constructs, a detailed understanding of their functioning as opto-genetical tools is still in its infancy. Here, we elucidate the early stages of the light-induced regulatory mechanism of LOV–TAP at the molecular level, using the noninvasive molecular dynamics simulation technique. More specifically, we find that Cys450-FMN-adduct formation in the AsLOV2-Jα-binding pocket after photoexcitation induces the cleavage of the peripheral Jα-helix from the LOV core, causing a change of its polarity and electrostatic attraction of the photoswitch onto the DNA surface. This goes along with the flexibilization through unfolding of a hairpin-like helix-loop-helix region interlinking the AsLOV2-Jα- and TrpR-domains, ultimately enabling the condensation of LOV–TAP onto the DNA surface. By contrast, in the dark state the AsLOV2-Jα photoswitch remains inactive and exerts a repulsive electrostatic force on the DNA surface. This leads to a distortion of the hairpin region, which finally relieves its tension by causing the disruption of LOV–TAP from the DNA. Proteins 2013. © 2012 Wiley Periodicals, Inc.

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