Capturing Transient Protein Structures on Multiple Spatial and Temporal Scales

 产品说明：金属蛋白在细胞中具有许多不同的功能，如储存和运输小分子底物、蛋白质、酶和信号转导蛋白。在这些金属蛋白中，金属氧化态/配位几何形状和整体蛋白质构象之间的相互作用在其功能中起着重要作用。该研究的长期目标是通过在不同的生物相关过程（如电子转移、配体结合和蛋白质折叠）中的高分辨率同步结构“快照”，对金属酶的金属活性位点结构与其功能之间的相关性获得新的认识。拟议中的研究旨在建立多个空间和时间尺度上的映射反应轨迹的仪器。利用X射线瞬态吸收（XTA，或瞬态X射线吸收光谱）光谱，以10-13秒（100 fs）到更长的时间分辨率，同时捕获一系列金属蛋白质中金属中心活性位点的瞬态电子和核结构，而蛋白质构象沿着反应坐标的变化可以通过X射线瞬态散射（XTS）捕获。该方法使用激光脉冲泵来触发生物反应，该生物反应可以是配体/抑制剂的直接光解离或金属活性位点处的光诱导氧化还原反应，其随后触发蛋白质构象变化，并且使用X射线脉冲来探测活性位点结构和蛋白质的构象，作为激光和X射线脉冲之间的延迟时间的函数。拟议的研究重点是建立一个便携式和多功能的样品室/检测设置，使酶促反应过程中的金属蛋白的本地/远程结构的同时检测。拟议的设置将建立在现有的X射线设施上，配备先进的探测器和激光系统，以满足蛋白质样品的特定需求。一旦仪器建成，它将成为便携式仪器的一部分，用于在其他光源中进行实验，例如具有飞秒脉冲X射线的线性相干光源（LCLS），以及与其他用户共享仪器的一部分。三个金属蛋白质系统将使用通过拟议的工作建立的仪器进行研究：1）金属结合位点结构和蛋白质构象的细胞色素c在折叠/重折叠; 2）构象门控的电子转移的杂交血红蛋白;和3）在过氧化氢酶的瞬时活性位点结构。这些结构结果与其他瞬态光谱测量的反应动力学结果相结合，将提供更深入的了解酶促反应过程中蛋白质内部的能量传递，并指导通过活性位点周围的结构修饰来调节蛋白质功能，这将导致酶功能增强，催化以及理论计算的进展。

 DESCRIPTION: Metalloproteins have many different functions in cells, such as storage and transport of small molecular substrates, proteins, enzymes and signal transduction proteins. In these metalloproteins, the interplay between the metal oxidation state/coordination geometry and the overall protein conformation plays important roles in their functions. The long term objective of the proposed research is to gain new insight into correlations between metal active site structures of a metalloenzyme and their functions through high resolution simultaneous structural "snapshots" during different biological relevant processes, such as electron transfer, ligand binding and protein folding. The proposed research aims at building instrumentation for mapping reaction trajectories on multiple spatial and temporal scales. Transient electronic and nuclear structures of metal centered active sites in a series of metalloproteins will be simultaneously captured using X-ray transient absorption (XTA, or transient X-ray absorption spectroscopy) spectroscopy with time resolutions from 10-13 second (100 fs) to longer, while the protein conformation change along the reaction coordinates can be captured by X-ray transient scattering (XTS). The method uses a laser pulse pump to trigger a biological reaction, which can be direct photodissociation of ligands/inhibitors or photoinduced redox reaction at metal active sites that subsequently triggers protein conformation changes, and an X-ray pulse to probe the active site structures and the conformations of proteins as a function of the delay time between the laser and X-ray pulses. The proposed research focuses on building a portable and multifunctional sample chamber/detection setup to enable simultaneous detection of the local/long range structures of metalloproteins during enzymatic reactions. The proposed setup will be built upon an existing X-ray facility with advanced detectors and laser systems to fulfill specific needs for protein samples. Once the instrumentation is built, it will be a part of portabl instrumentation for conducting experiments in other light sources, such as the linear coherence light source (LCLS) with femtosecond pulsed X-rays, and a part of shared instrumentation with other users. Three metalloprotein systems will be investigated using the instrumentation built through the proposed work: 1) metal binding site structures and protein conformations of cytochrome c during folding/refolding; 2) conformation gating in electron transfer of hybrid hemoglobins; and 3) transient active site structures in catalase. These structural results combined with those of reaction kinetics from other transient spectroscopic measurements will provide much deeper understanding of energy transduction inside the proteins during enzymatic reactions and guidance for modulating protein functions via structural modifications around the active sites, which will lead to advances in enzymatic function enhancement, catalysis, as well as theoretical calculations.