MECHANISMS OF POLYSIALIC ACID ASSEMBLY IN E COLI

现在有充分的证据表明，细胞表面的大分子结构 由大多数微生物物种表达，介导多种重要的 控制细胞如何与它们的 环境 因此，对这些相互作用的明确描述将 对于更全面地了解分子基础是必要的 致病性 在许多细胞表面结构中， 细菌，多糖可能是结构上最多样化的， 毫无疑问，这些分子代表了细胞的最外层， 可以与环境进行交互。 很明显 进一步了解传染病的分子机制 这些过程需要对基因和基因产物有详细的了解， 其参与细胞表面多糖的合成和组装。 为了以可管理的方式处理这个问题，注意力集中在 大肠杆菌K1抗原。 K1抗原是由许多 作为200个唾液酸残基，其形成无支链的均聚物链 附着在细胞膜上 唾液酸是如何合成的， 组装，并从其内部合成位点转移， 因此，膜到它们在外膜处的最终位置代表 这是一个在分子生物学和 膜组件的比表面积。 当前的研究目标需要 描述参与K1的基因的组织 抗原生物合成 通过使用重组DNA技术，这些 已经在DNA的30至35个内切酶片段上分离出基因， 定义了一个复杂的基因位点簇， 合成和用于聚合物组装。 经典遗传算法的应用 重组DNA技术将揭示这个基因簇的细节， 其调节及其在指导K1抗原生物合成中的功能， 表情

It is now amply documented that cell surface macromolecular structures expressed by most microbial species mediate a variety of important physiological processes which govern how cells interact with their environment. An explicit description of these interactions will therefore be necessary for a more complete understanding of the molecular basis of pathogenicity. Among the many cell surface structures expressed by bacteria, polysaccharides are perhaps the most structurally diverse, and undoubtedly these molecules represent the outermost layer of the cell that is available for interaction with the environment. It is clear that further understanding of the molecular mechanisms of infectious disease processes will require detailed knowledge of the genes and gene products which participate in cell surface polysaccharide synthesis and assembly. To approach this problem in a manageable way, attention has been focused on the K1 antigen of Escherichia coli. The K1 antigen is composed of as many as 200 sialic acid residues which form unbranched homopolymeric chains attached to the cell envelope. How sialic acids are synthesized, assembled, and translocated from their site of synthesis at the inner membrane to their final location at the outer membrane therefore represents a problem of fundamental importance in molecular biology and in the specific area of membrane assembly. Immediate research aims require a description of the organization of the genes which participate in K1 antigen biosynthesis. By the use of recombinant DNA techniques, these genes have been isolated on a 30 to 35 kilobase fragment of DNA that defines a complex cluster of gene loci that are required for sialic acid synthesis and for polymer assembly. Application of classical genetic and recombinant DNA techniques to this gene cluster will reveal the details of its regulation and of its function in directing K1 antigen biosynthesis and expression.