SIGNALING STATE OLIGOMERIZATION OF THE SLR1694 BLUF DOMAIN DURING PHOTOCYCLE

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 中心，不一定是研究者的机构。 所有生物体都有能力对生物刺激做出反应，例如光、电压、氧气、配体和环境因素。当施加时，每种刺激在几个步骤中转化为特定的细胞反应，从而促进信号转导途径。为了理解信号转导的工作机制，重要的是要识别参与信号传导的分子单位，例如刺激受体。 在这些刺激中，光在广泛的生物学重要细胞反应中起着重要作用，包括光合作用和基因表达（1）。到目前为止，已经确定了六种光感受器（2）。在这些光感受器中，BLUF结构域是最近发现的，因此研究程度有限。特别地，Slr 1694 BLUF结构域在溶液中作为同源二聚体存在，但在黑暗中寡聚形成十聚体。这种推定的信号传导状态是光学惰性的，其形成动力学不易于使用时间分辨光谱法（例如，瞬态吸收（TA）光谱法）探测。相比之下，时间分辨X射线散射技术对结构变化敏感，而不管感兴趣状态的光学活性如何。例如，时间分辨小角X射线散射（TR-SAXS）对溶液中蛋白质的大小和形状等全局结构变化敏感，而时间分辨广角X射线散射（TR-WAXS）提供了关于具有全局灵敏度的蛋白质的三级和四级结构变化的丰富信息。因此，时间分辨X射线散射技术适合于探测BLUF结构域蛋白中信号状态形成的结构动力学。在这里，我们提出的时间分辨实验的Slr 1694 BLUF结构域蛋白使用TR-SAXS和TR-WAXS技术，以调查的光化学反应导致的信号状态的形成的机制。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. All living organisms have an ability to respond to biological stimuli such as light, voltage, oxygen, ligands and environmental factors. When applied, each stimulus is converted into a specific cellular response in several steps contributing to signal-transduction pathway. To understand the working mechanism of signal transduction, it is important to identify the molecular units involved in signaling, for example, stimuli receptors. Among the stimuli, light plays an important role in a wide range of biologically important cellular responses including photosynthesis and gene expression (1). Thus far, six kinds of photoreceptors have been identified (2). Among these photoreceptors, the BLUF domain was discovered recently, thus having been studied to a limited extent. In particular, the Slr1694 BLUF domain exists as a homo dimer in solution, but oligomerizes in the dark to form a decamer. This putative signaling state is optically inactive that its formation dynamics is not readily probed using time-resolved optical spectroscopy, for example, transient absorption (TA) spectroscopy. In contrast, time-resolved X-ray scattering techniques are sensitive to the structural changes regardless of the optical activity of the state of interest. For example, time-resolved small-angle X-ray scattering (TR-SAXS) is sensitive to global structural changes such as size and shape of a protein in solution, while time-resolved wide-angle X-ray scattering (TR-WAXS) provides rich information about tertiary and quaternary structural changes of a protein with global sensitivity. Therefore, time-resolved X-ray scattering techniques are suitable for probing the structural dynamics of the signaling state formation in the BLUF domain proteins. Here, we propose the time-resolved experiments on the Slr1694 BLUF domain proteins using TR-SAXS and TR-WAXS techniques to investigate the mechanism of photochemical reaction leading to the formation of signaling state.