PSEUDOMONAS AERUGINOSA EXOTOXIN A

铜绿假单胞菌外毒素A 分子量66,583是一个重要的毒力因子 假单胞菌感染。毒素也是一种模型系统 杂合毒素的制备及性质研究 癌症化疗的临床重要性。有四个步骤 在毒素的作用机制中。首先，毒素与细胞结合。 哺乳动物细胞的表面受体。第二，毒素是 内吞并暴露在内胞内的低pH中 车厢。第三，携带病毒的一部分 催化中心穿透囊泡的膜并进入 细胞质。第四，这种毒素能催化抑制蛋白质 综合。对分子和细胞的三条研究路线 这里提出了外毒素A的生物学特性： 1.外毒素A基因表达的研究一个 毒素基因表达的可能激活剂的结合部位是 呈现在结构基因的上游。我们建议确定 并对其作用机理进行了表征。 2.结构微球的制备与表征 我们对外毒素A的变种特别感兴趣 不能与受体相互作用的变体，因为它们应该 是混合毒素的有用成分。我们还打算搜索 对于与受体结合但不是的变体 细胞毒性，因为它们不能穿透膜泡 内吞作用。 3.杂合毒素的构建和鉴定。 不能与受体相互作用的外毒素A变体将是 偶联到可替代的受体结合配体。这些属性 将对混合毒素进行研究，并将其潜在地 将对消除肿瘤细胞进行评估。

Exotoxin A of Pseudomonas aeruginosa, a protein of molecular weight 66,583, is an important virulence factor in Pseudomonas infections. The toxin is also a model system for preparation and characterization of hybrid toxins that may have clinical importance in cancer chemotherapy. There are four steps in the mechanism of toxin action. First, the toxin binds to cell surface receptors on mammalian cells. Second, the toxin is endocytosed and exposed to a low pH within the endocytic compartment. Third, a portion of the toxin that carries the catalytic center penetrates the membrane of a vesicle and enters the cytoplasm. Fourth, the toxin catalytically arrests protein synthesis. Three lines of research into the molecular and cell biology of exotoxin A are proposed here: 1. Investigation of exotoxin A gene expression. A binding site for a putative activator of toxin gene expression is present upstream of the structural gene. We propose to identify the activator and characterize its mechanism of action. 2.Preparation and characterization of structurally altered variants of exotoxin A. We are particularly interested in variants that fail to interact with receptors because they should be useful components of hybrid toxins. We also intend to search for variants that bind to receptors but are nevertheless not cytotoxic because they fail to penetrate a membrane vesicle after endocytosis. 3.Construction and characterization of hybrid toxins. Exotoxin A variants that fail to interact with receptors will be coupled to alternative receptor-binding ligands. The properties of the hybrid toxins will be studied and their potential to eliminate tumor cells will be assessed.