DIFFRACTION OF BACTERIAL ENDOTOXINS: STRUCT BASED DRUG DESIGN, SCREEN PCP ENZYME

δ内毒素是芽孢杆菌产生的杀虫剂 苏云金杆菌亚种 库斯塔基 这些毒素以原毒素的形式产生 (135 kDa），并通过它们的 孢子囊中的双嘧啶晶体形式。 当摄入 鳞翅目幼虫晶体溶解并被蛋白水解 消化成活性毒素形式（60-65 kDa）。 这种激活的毒素 能够打开昆虫上皮中的K+通道 中肠 离子泄漏最终导致 昆虫的中肠和死亡。 最近，一种新的活性形式 毒素CryIIIB 2的分子量为64 kDa。 细菌 内毒素CryIIIB 2是一种652个残基的蛋白质， 正交晶系空间群C2221，晶胞维数a = 122.44，B = 131.81，c = 105.37，并且含有一个不对称分子 单位 采用同步辐射技术采集了2.2级分辨率的数据 1997年12月在康奈尔大学的国际象棋设施， Vivian Cody和Nikolai Galitsky为EC 11095的复合体设计， D-半乳糖胺 虽然这些数据并不一致， 到高分辨率，Walt Pangborn能够至少 50%完成所有外壳到2.2和分辨率。 的结构 天然CryIIIB 2用作旋转的搜索模型， 翻译功能的程序XPLOR，其中显示没有 分子取向的显著变化 与室温模型相比。 低的主要后果 温度数据收集是单位单元沿着的收缩 a和B晶格方向。 差异的解释 电子密度图由3.0&细化模型的 CryIIIB 2的Arg-348突变体显示了大的密度分布， 显然不是一种溶剂，它可以适合 糖 这些数据表明，半乳糖胺位于 CryIIIB 2的三个结构域的交叉。 改进这些 2.2和分辨率的数据表明其他潜在的糖结合位点 是可能的。

Delta endotoxins are the entomocidal agent produced by Bacillus thuringiensis ssp. Kurstaki. These toxins are produced as protoxins (135 kDa) by the bacteria during sporulation and recognized by their bipyrimidal crystalline form in the sporangium. When ingested by larval Lepidoptera the crystal dissolves and is proteolytically digested to the active toxin form (60-65 kDa). This activated toxin is capable of opening K+ channels in the epithelium of the insect midgut. Ion leakage ultimately results in the complete disruption of the midgut and death of the insect. More recently, a new active form of the toxin, CryIIIB2, has been determined (64 kDa). The bacterial endotoxin CryIIIB2 is a 652 residue protein which crystallizes in the orthorhombic space group C2221 with unit cell dimensions a = 122.44, b = 131.81, and c = 105.37& and contain one molecule in the asymmetric unit. Synchrontron radiation was used to collect 2.2& resolution data at the CHESS facility at Cornell University in December, 1997 by Vivian Cody and Nikolai Galitsky for the complex of EC11095 with D-galactosamine. Although these data were did not diffract uniformly to high resolution, Walt Pangborn was able to scale data with at least 50% completion for all shells to 2.2& resolution. The structure of the native CryIIIB2 was used as a search model for the rotation and translation function in the program XPLOR which revealed there was no significant change in the molecular orientation of the molecule compared to the room temperature model. The major consequence of low temperature data collection is the contraction of the unit cell along the a and b lattice directions. Interpretation of the difference electron density maps made from the 3.0& refinement model of the Arg-348 mutant of CryIIIB2 revealed a large density profile that clearly was not a cluster of solvent and that could be fit to the sugar. These data reveal that the galactosamine is positioned at the intersection of the three domains of CryIIIB2. Refinement of these data to 2.2& resolution suggest other potential sugar binding sites are possible.