P2L HIGH RESOLUTION STUDY

而天然的p21-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，R-Syms和R-Cryst的曲线图都是平滑的，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， 初步的闪冻试验表明， 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。 分辨率极限有望远低于IA.数据收集 BioCARS站14-BM-D。

While native p2l-ras is an essential growth-regulating component of eukaryotic cells, 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 limit of resolution hopefully well below I A. Data collection on BioCARS Station 14-BM-D.