STRUCTURE AND INTERACTION OF PROTEINS WITH MEMBRANES

我们正在研究与之相互作用的蛋白质的结构 真核细胞表面，以及蛋白质被 被细胞内化。小麦胚芽凝集素(WGA)，是一种植物凝集素 结合到细胞表面的碳水化合物，正在用x射线进行研究 结晶学和化学方法。对其作用机制的研究 胞外蛋白的内化及其化学效应 白喉毒素(DT)的细胞毒性正在进行修饰。 根据最近确定的氨基酸序列和额外的高 WGA 2的分辨率X射线数据，一个重建和改进的模型 WGA结构将用于分析亚单位相互作用和 糖类与蛋白质结合的立体化学。氨基酸 将确定WGA异凝素1的序列，并通过模型建立， 决定差异糖的那些官能团 确定了这两种异位凝集素的亲和力。最后，水晶 WGA-2与主红糖肽的络合物结构 血细胞膜蛋白，血糖素，将被测定 结晶学上的。这个建筑群的结构将是一个更 蛋白质-细胞表面糖相互作用的最终模型比 较小的糖类复合体。DT与DT相互作用的本质 几种细胞系在培养过程中的细胞表面群及其要求 对于DT有毒A链的内化将用化学方法进行研究 方法：研究方法。DT结合的细胞表面分子将被确定 通过化学修饰研究，并通过使用特定的 细胞生物合成过程的抑制剂。化学修饰的DT将 用于表征膜转运过程，并用于分离 进行运输的膜结合分子。类似 将测试改良的胰岛素原或其他激素，以确定 在它们的内化过程中也使用了相同的机制。这些研究 关于膜结构和运输的问题。这些结构 膜表面分子的数量受到恶性等因素的影响 转化、细胞微数和细胞密度，控制黏附和 装配工艺。细胞膜转运决定了细胞内 细胞的状态，并在效果中与细胞表面结构相联系 激素、病毒、抗体和毒素与受体结合。它 也可能在治疗药物的细胞内递送中得到应用 探员们。

We are studying the structure of proteins which interact with the eukaryotic cell surface, and the mechanism by which proteins are internalized by cells. Wheat germ agglutinin (WGA), a plant lectin which binds to cell surface carbohydrates, is being studied by x-ray crystallography and chemical methods. Studies of the mechanism of internalization of extracellular proteins and the effects of chemical modification of cytotoxicity are being done on diphtheria toxin (DT). Based on the recently determined amino acid sequence and additional high resolution x-ray data for WGA 2, a reconstructed and refined model of the WGA structure will be used for analysis of subunit interactions and stereochemistry of saccharide binding to the protein. The amino acid sequence of WGA isolectin 1 will be determined, and by model building, those functional groups which determine the differential saccharide affinities of these two isolectins determined. Finally, the crystal structure of a complex of WGA 2 with a glycopeptide from the major red blood cell membrane protein, glycophorin, will be determined crystallographically. The structure of this complex will be a more definitive model for protein-cell surface saccharide interactions than the smaller saccharide complexes. The nature of the interaction of DT with cell surface groups of several cell lines in culture, and the requirements for internalization of the toxic A-chain of DT will be studied by chemical methods. The cell surface molecules to which DT binds will be determined by chemical modification studies, and through the use of specific inhibitors of cellular biosynthetic processes. Chemically modified DT will be used to characterize the membrane translocation process, and to isolate the membrane-bound molecules which carry out the transport. Similarly modified proinsulin or other hormones will be tested to determine whether the same mechanism is utilized in their internalization. These studies bear on the question of membrane structure and transport. The structures of membrance surface molecules are influenced by factors such as malignant transformation, cellular millieu and cell density, and control adhesion and assembly processes. Cellular membrane transport determines the internal state of the cell, and is linked to cell surface structure in the effects of hormones, viruses, antibodies and toxins upon binding to receptors. It may also find application in the intracellular delivery of therapeutic agents.