Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan.
Sci Rep. 2021 Jun 7;11(1):11995. doi: 10.1038/s41598-021-91497-5.
Light-Oxygen-Voltage (LOV) domains are responsible for detecting blue light (BL) and regulating the activities of effector domains in various organisms. Photozipper (PZ), an N-terminally truncated aureochrome-1 protein, contains a LOV domain and a basic leucin zipper (bZIP) domain and plays a role as a light-activatable transcription factor. PZ is monomeric in the dark state and undergoes non-covalent dimerization upon illumination with BL, subsequently increasing its affinity for the target DNA. To clarify the molecular mechanism of aureochromes, we prepared site-directed mutants of PZ and performed quantitative analyses in the dark and light states. Although the amino acid substitutions in the hinge region between the LOV core and A'α helix had minor effects on the dimerization and DNA-binding properties of PZ, the substitutions in the β-sheet region of the LOV core and in the A'α helix significantly affected these properties. We found that light signals are transmitted from the LOV core to the effector bZIP domain via the hydrophobic residues on the β-sheet. The light-induced conformational change possibly deforms the hydrophobic regions of the LOV core and induces the detachment of the A'α helix to expose the dimerization surface, likely activating the bZIP domain in a light-dependent manner.
光氧电压（LOV）结构域负责检测蓝光（BL）并调节各种生物体中效应结构域的活性。Photozipper（PZ）是一种 N 端截断的 aureochrome-1 蛋白，包含一个 LOV 结构域和一个碱性亮氨酸拉链（bZIP）结构域，作为一种光激活转录因子发挥作用。PZ 在黑暗状态下是单体，在受到 BL 照射时会发生非共价二聚化，随后增加其与靶 DNA 的亲和力。为了阐明 aureochrome 的分子机制，我们制备了 PZ 的定点突变体，并在黑暗和光照状态下进行了定量分析。尽管 LOV 核心和 A'α 螺旋之间铰链区域的氨基酸取代对 PZ 的二聚化和 DNA 结合特性的影响较小，但 LOV 核心的β-折叠区域和 A'α 螺旋中的氨基酸取代对这些特性有显著影响。我们发现，光信号通过β-折叠上的疏水残基从 LOV 核心传递到效应 bZIP 结构域。光诱导的构象变化可能会使 LOV 核心的疏水区域变形，并导致 A'α 螺旋脱离，暴露二聚化表面，可能以光依赖的方式激活 bZIP 结构域。
