MAD DATA COLLECTION FROM CRYSTALS OF PLZF BTB & POZ &GCN5

四膜虫p55蛋白及其人和酵母同源物 （分别为hGCN 5和yGCN 5）是转录衔接蛋白 参与转录激活和核酶体 不稳定 这两种活动最近都被证明是 严格依赖于p55乙酰化组蛋白的能力 核小体的组成部分。 p55的区域赋予了这个 活性已经被映射到保守的酶HAT（对于组蛋白 乙酰转移酶）结构域。 我们的实验室一直对 这一活动背后的结构基础。 帮助提供见解 HAT结构域的结构和功能，我们准备了 来自p55的HAT结构域的晶体。 晶体以嘧啶的形式生长 典型尺寸为0.3 x 0.2 x 0.2 mm， 分辨率至少为2.2
使用旋转阳极X射线源。 对这些晶体的表征表明，它们属于 原始单斜晶胞，P31或P32，晶胞尺寸a=B=64.10
，c=97.80
. CHESS的可用射束时间（1998年4月29日至1998年5月1日， 光束线F-2）允许我们收集完整的1.8
MAD数据集来自 p55 HAT结构域的硒代甲硫氨酸衍生晶体。 为 数据收集我们使用3个波长（12600 eV、12658 eV和12662 eV eV），并获得了2 × 120，在每个 波长 用DPS/MOSFILM处理数据表明， 高质量（Rsym < 4%至1.8
对于每个波长）。 我们 目前使用差分帕特森和差分傅立叶技术 以定位和细化用于MAD定相的重原子位置。 由于 由于光束停机时间的限制，我们无法完成我们的 PLZF-BTB/POZ晶体的MAD数据集。

The tetrahymena p55 protein and its human and yeast homologues (hGCN5 and yGCN5, respectively), are transcriptional adaptor proteins that are involved in both transcriptional activation and nucleasome destabilization. Both of these activities have been recently shown to be strictly dependent on the ability of p55 to acetylate the histone components of nucleasomes. The region of p55 that confers this activity has been mapped to a conserved enzymatic HAT (for histone acetyltransferase) domain. Our laboratory has been interested in the structural basis underlying this activity. To help provide insights into the structure and function of HAT domains, we have prepared crystals of the HAT domain from p55. The crystals grow as pyrimides with typical dimensions of 0.3 x 0.2 x 0.2 mm, and diffract X-rays to a resolution of at least 2.2
using a rotating anode X-ray source. Characterization of these crystals show that they belong to a primitive monoclinic cell, P31 or P32, with cell dimensions a=b=64.10
, and c=97.80
. The available beamtime at CHESS (4/29/98-5/1/98 on beamline F-2) allowed us to collect a complete 1.8
MAD data set from seleno-methionine derivatized crystals of the p55 HAT domain. For the data collection we used 3 wavelengths (12600 eV, 12658 eV and 12662 eV) with the inverse-beam method and obtained 2 x 120,of data at each wavelength. Processing of the data with DPS/MOSFILM shows that it is of high quality (Rsym < 4% to 1.8
for each wavelength). We are currently using difference Patterson and difference Fourier techniques to locate and refine the heavy atom positions for MAD phasing. Due to time limitations due to beam downtime we were unable to complete our MAD data set for the PLZF-BTB/POZ crystals.