Elucidating the signal transduction mechanism of the blue-light-regulated photoreceptor YtvA: From photoactivation to downstream regulation

YongLe He, Jinnette Tolentino Collado, James N. Iuliano, Helena A. Woroniecka, Christopher R. Hall, Agnieszka A. Gil, Sergey P. Laptenok, Gregory M. Greetham, Boris Illarionov, Adelbert Bacher, Markus Fischer, Jarrod B. French, Andras Lukacs, Stephen R. Meech, Peter J. Tonge

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The blue-light photoreceptor YtvA from Bacillus subtilis has an N-terminal flavin mononucleotide (FMN)-binding light-oxygen-voltage (LOV) domain that is fused to a C-terminal sulfate transporter and anti-σ factor antagonist (STAS) output domain. To interrogate the signal transduction pathway that leads to photoactivation, the STAS domain was replaced with a histidine kinase, so that photoexcitation of the flavin could be directly correlated with biological activity. N94, a conserved Asn that is hydrogen bonded to the FMN C2═O group, was replaced with Ala, Asp, and Ser residues to explore the role of this residue in triggering the structural dynamics that activate the output domain. Femtosecond to millisecond time-resolved multiple probe spectroscopy coupled with a fluorescence polarization assay revealed that the loss of the hydrogen bond between N94 and the C2═O group decoupled changes in the protein structure from photoexcitation. In addition, alterations in N94 also decreased the stability of the Cys-FMN adduct formed in the light-activated state by up to a factor of ∼25. Collectively, these studies shed light on the role of the hydrogen bonding network in the LOV β-scaffold in signal transduction.
Original languageEnglish
Pages (from-to)696-706
Number of pages11
JournalACS Chemical Biology
Issue number3
Early online date22 Feb 2024
Publication statusPublished - 15 Mar 2024

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