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Regulatory mechanism of the light‐activable allosteric switch LOV–TAP for the control of DNA binding: A computer simulation study
Author(s) -
Peter Emanuel,
Dick Bernhard,
Baeurle Stephan A.
Publication year - 2013
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.24196
Subject(s) - photoswitch , biophysics , chemistry , allosteric regulation , dna , repressor , microbiology and biotechnology , biochemistry , biology , gene , transcription factor , photochemistry , receptor
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.