Department of Chemistry, Graduate School of Science, Kyoto University, Japan.
J Am Chem Soc. 2012 May 23;134(20):8336-9. doi: 10.1021/ja301540r. Epub 2012 May 11.
PixD (Slr1694) is a blue light receptor that contains a BLUF (blue light sensors using a flavin chromophore) domain. A protein-protein interaction between PixD and a response regulator PixE (Slr1693) is essential to achieve light signal transduction for phototaxis of the species. Although the initial photochemical reaction of PixD, the red shift of the flavin absorption spectrum, has been investigated, the subsequent reaction dynamics remain largely unresolved. Only the disassembly of the PixD(10)-PixE(5) dark complex has been characterized by static size exclusion chromatography. In this report, interprotein reaction dynamics were examined using time-resolved transient grating spectroscopy. The dissociation process was clearly observed as the light-induced diffusion coefficient change in the time domain, and the kinetics was determined. More strikingly, disassembly was found to take place only after photoactivation of two PixD subunits in the complex. This result suggests that the biological response of PixD does not follow a linear correlation with the light intensity but appears to be light-intensity-dependent.
PixD（Slr1694）是一种蓝光受体，含有 BLUF（使用黄素辅基的蓝光传感器）结构域。PixD 与响应调节子 PixE（Slr1693）之间的蛋白-蛋白相互作用对于该物种的光趋性的光信号转导是必不可少的。尽管已经研究了 PixD 的初始光化学反应，即黄素吸收光谱的红移，但随后的反应动力学在很大程度上仍未得到解决。仅通过静态排阻层析法对 PixD（10）-PixE（5）暗复合物的解组装进行了表征。在本报告中，使用时间分辨瞬态光栅光谱法研究了蛋白质间的反应动力学。可以在时域中观察到光诱导的扩散系数变化清楚地观察到离解过程，并且确定了动力学。更引人注目的是，仅在复合物中的两个 PixD 亚基光激活后才发现解组装。这一结果表明，PixD 的生物学反应与光强之间并非呈线性相关，而是似乎依赖于光强。
