title: Regulatory mechanism of the light-activable allosteric switch LOV-TAP for the control of DNA binding: a computer simulation study.
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.
authors.affiliation: Department of Chemistry and Pharmacy, Institute of Physical and Theoretical Chemistry, University of Regensburg, Regensburg D-93040, Germany.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Peter
authors.forename: Bernhard
authors.initials: B
authors.lastname: Dick
authors.forename: Stephan A
authors.initials: SA
authors.lastname: Baeurle
mesh_terms: D000494:Allosteric Regulation; D018554:Avena / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D003545:Cysteine / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005486:Flavin Mononucleotide / Q000235:genetics / Q000378:metabolism; D008027:Light; D056004:Molecular Dynamics Simulation; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D055668:Photochemical Processes; D056949:Phototropins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D055672:Static Electricity; D013997:Time Factors; D029968:Escherichia coli Proteins
chemical_list: D001426:Bacterial Proteins; D003545:Cysteine; D004268:DNA-Binding Proteins; D005486:Flavin Mononucleotide; D046912:Multiprotein Complexes; D056949:Phototropins; D012097:Repressor Proteins; C027190:TRPR protein, E coli; D029968:Escherichia coli Proteins