P2L HIGH RESOLUTION STUDY

而天然的p2i-ras是一种重要的生长调节成分 在真核细胞中，单点突变足以转化为 细胞形成一种促进肿瘤的癌蛋白。在一次高潮中 在人类肿瘤中，三个内源性ras基因之一的百分比是 由体细胞点突变激活。激活基因突变 原则可能会干扰这两种调节机制： 核苷酸交换增强或GTP水解酶急剧增加 放慢了速度。在过去的几年里，X射线衍射研究在 P21对结构和结构的理解有很大贡献 这种小的GTP结合蛋白的作用机制。该结构 P21-ras的GppNHp复合体在1.35A被提纯 决议。在光子工厂进行的初步实验 日本筑波的同步加速器指出，衍射数据可能是 收集到比我A更好的分辨率，有一个微弱的信号 0.9A和R-Syms的曲线图。和R-Cryst是平滑的，分辨率为 1.1A.数据是在非最佳条件下收集的， 晶体没有被冻结，所以辐射损伤是一个问题，我们的 必须对不完整的数据集进行分析。与此同时， 初步的闪速冷冻测试表明， 晶体可以在尽可能不降低分辨率的情况下被冻结 在旋转阳极源上进行评估。这是有帮助的，水晶 实际上是在低温保护剂溶液中生长的。我们将致力于 测量这种晶体的衍射图。 分辨率限制，希望远低于IA。数据收集关于 BioCARS站14-BM-D。

While native p2 I -ras is an essential growth-regulating component of eukaryoticcells, single point mutations are sufficient to convert the cellular form into a tumor promoting oncoprotein. In a high percentage of human tumors, one of the three endogenous ras genes is activated by a somatic point mutation. Activating mutations in principle can interfere with both regulating mechanisms: either nucleotide exchange is enhanced or GTP-hydrolysis is drastically slowed down. Over the past few years, X-ray diffraction studies on p2l have contributed greatly to the understanding of the structure and mechanism of action of this small GTP-binding protein. The structure of the GppNHp complex of p2l-ras has been refined at 1.35 A resolution. Preliminary experiments performed at the Photon Factory synchrotron, Tsukuba, Japan, indicate that diffraction data might be collected to better than I A resolution, there was a weak signal to 0.9 A and plots of R-syms. and R-cryst were smooth to a resolution of 1. 1 A. The data were collected under non-optimal conditions and the crystals were not frozen, so radiation damage was a problem and our analysis had to be done on incomplete data sets. In the meantime, preliminary flash freezing tests have been done showing that the crystals can be frozen without loosing resolution as far as can be assessed on a rotating anode source. It is helpful that the crystals are actually grown in a cryo-protectant solution. We will aim to measure diffraction the diffraction pattern of such a crystal to the limitof resolution, hopefully well below I A. Data collection on BioCARS Station 14-BM-D.