X-RAY STRUCTURES OF PENTAMERIC ION CHANNELS IN THE ABSENCE AND PRESENCE OF ANEST

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 研究中心，而研究中心不一定是研究者所在的机构。 全身麻醉的分子机制仍然是一个谜。虽然五聚体配体门控离子通道（pLGIC）的超家族已被确定为全身麻醉剂的假定目标，这些pLGIC的高分辨率结构的缺乏阻碍了了解麻醉剂结合位点在这些蛋白质中以及麻醉剂结合如何影响蛋白质功能。最近出现了一个令人兴奋的获得答案的平台，因为pLGIC家族的两种细菌同系物GLIC和ELIC的X射线结构以2.9和3.3的分辨率得到解决。作为阳离子通道，GLIC和ELIC可以分别在开放和闭合通道状态下结晶。类似于哺乳动物pLGIC阳离子通道，GLIC的阳离子电导可以被多种麻醉剂在亚临床剂量下抑制。在这里，我们建议与全身麻醉剂共结晶GLIC和ELIC。过去没有麻醉剂与任何pLGIC一起结晶。GLIC-和ELIC-麻醉剂复合物的X射线结构将为解释全身麻醉剂对pLGIC的功能影响提供新的结构基础。选择吸入麻醉剂氟烷和静脉麻醉剂硫喷妥钠和氯胺酮进行研究。我们在没有和存在麻醉剂的情况下结晶了GLIC和ELIC。我们的初步数据表明，在硫喷妥钠和氯胺酮的存在下，GLIC的分辨率达到2.7 <$和2.9 <$。尽管有形的蛋白质分辨率，以确定精确的麻醉剂结合位点的蛋白质仍然具有挑战性，因为小的麻醉剂分子大小和相对较低的麻醉剂结合亲和力（~100？M）。因此，我们要求使用特定的光束线，提供高灵敏度和分辨率的溴，硫，并可能氯原子。这些原子包含在选定的麻醉剂中，可以作为蛋白质麻醉复合物中麻醉剂的标记。

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. The molecular mechanism of general anesthesia remains an enigma. Although a superfamily of pentameric ligand gated ion channels (pLGICs) has been identified as putative targets of general anesthetics, the lack of high-resolution structures of these pLGICs hinders the understanding where anesthetic binding sites are in these proteins and how anesthetic bindings impact on protein functions. An exciting platform for getting the answers has recently emerged as the x-ray structures of two bacterial homologs to the pLGIC family, GLIC and ELIC, were solved with resolutions of 2.9 and 3.3 ¿. As cation channels, GLIC and ELIC can be crystallized in the open- and close-channel states, respectively. Similar to mammalian pLGIC cation channels, cation conductance of GLIC could be inhibited by a variety of anesthetics at subclinical doses. Here we propose to co-crystallize GLIC and ELIC with general anesthetics. No anesthetic has been crystallized with any pLGICs in the past. The x-ray structures of GLIC- and ELIC-anesthetics complexes will provide novel structural basis to explain the functional impact of general anesthetics to the pLGICs. Inhaled anesthetic halothane and intravenous anesthetics thiopental and ketamine are chosen for the study. We have crystallized GLIC and ELIC in the absence and presence of anesthetics. Our preliminary data show that the resolutions up to 2.7 ¿ and 2.9 ¿ have been achieved for GLIC in the presence of thiopental and ketamine. Despite tangible protein resolutions, to define precise anesthetic binding sites in the proteins remains challenging because of small anesthetic molecular sizes and relatively low anesthetic binding affinities (~100 ?M). Thus, we request to use specific beamlines that provide high sensitivity and resolution to bromide, sulfur, and possibly chloride atoms. These atoms are contained in the selected anesthetics and can serve as marks for anesthetics in the proteinanesthetic complexes.