Structure of Rhodopsin and G-Protein Coupled Receptors

描述(申请者的描述)：愿景的第一步是 光与视紫质的相互作用，视紫红质是一种与光吸收结合的蛋白质 发色团，11顺式视网膜。光吸收导致视网膜从 顺式到反式构象变化，这种结构变化被传递 到周围的蛋白质。一系列蛋白质-蛋白质相互作用是 被结构变化改变，并诱导G蛋白级联， 最终导致神经冲动。这一过程得到了很好的研究， 它在人类感知和疾病中的作用是在基础水平上被理解的。 然而，视紫红质的三维原子级结构尚不清楚。 为人所知。这是因为这种蛋白质是一种跨膜受体。膜 蛋白质很难用核磁共振或X射线结晶学来研究， 后者是因为难以获得晶体。最近，水晶石 牛的视紫红质已经产生，这是这项提议的重点。X射线 已经开始使用这些晶体进行晶体结构分析，并进行了低 分辨率结构可用来确认存在七个 跨膜螺旋。在这个项目中，更多的有序晶体将被生长到 提供结构的更高分辨率视图，包括膜间 多肽环对于与G蛋白的相互作用很重要。陷于困境 视紫红质的光态，其几个具有改变生色团的衍生物， 对该蛋白质的突变也将进行结晶学研究。这些 三维分子结构将被用来关联 视紫红质及其相互作用的生化和生物物理信息 与其他分子结合。此外，这种第一种结构的G蛋白偶联 受体将为该基因其他成员的同源建模提供基础 具有重要药用价值的蛋白质家族。

Description (applicant's description): The first step in vision is the interaction of light with rhodopsin, a protein bound to a light absorbing chromophore, 11-cis retinal. Photo absorption causes retinal to convert from a cis to trans conformational change, and this change in structure is transmitted to the surrounding protein. A series of protein-protein interactions are altered by the structural change, and a G-protein cascade is induced, eventually leading to a nerve impulse. This process is very well studied and its role in human perception and disease is understood at the basic level. However, the three-dimensional, atomic level structure of rhodopsin is not yet known. This is because the protein is a transmembrane receptor. Membrane proteins are very difficult to study using NMR or X-ray crystallography, the latter because of difficulties in obtaining crystals. Recently, crystals of bovine rhodopsin have been generated that are the focus of this proposal. X-ray crystal structure analysis has been initiated using these crystals, and a low resolution structure is available confirming the presence of seven transmembrane helices. In this project, more ordered crystals will be grown to provide a higher resolution view of the structure, including the inter-membrane polypeptide loops important for interactions with G-proteins. Trapped photostates of rhodopsin, several of its derivatives with altered chromophores, and mutants for the protein will also be studied crystallographically. These three-dimensional molecular structures will be used to correlate the biochemical and biophysical information about rhodopsin and its interactions with other molecules. In addition, this first structure of a G-protein coupled receptor will provide a base for homology modeling of other members of this pharmaceutically important protein family.