BIOSYNTHESIS OF YEAST CELL WALL BETA 1,6 GLUCAN POLYMERS

描述：（申请人描述的逐字）在酵母和其他 真菌，细胞形状，生长和细胞分裂取决于协调的 细胞壁组分的合成和降解。一个数量上的小，但 酵母细胞壁的功能关键组分是聚合物β-1，6 葡聚糖。这种多糖与其他细胞壁共价交联 组分，如几丁质、3'-1，3葡聚糖和甘露糖蛋白。这些交叉连接 稳定和组织细胞壁。该项目的长期目标是 研究β-1，6葡聚糖的合成机制， 与其他细胞壁成分相关。我们假设， β-1，6的合成不同于更丰富的3'-1，3葡聚糖的合成 聚合物的具体来说，拟议的工作将审查的假设， β-1，6葡聚糖的合成起始于内质网的内腔， 网状细胞。链的延长和分支发生在高尔基体， 组装的聚合物被包装到分泌囊泡中， 周质空间和组装成细胞壁。在以前的工作中， 证明了UDP-葡萄糖的转运，UDP-葡萄糖是聚合物的糖供体 组装，进入酵母的内质网腔 啤酒。为了验证我们的假设，我们将确定UDP-葡萄糖 酵母中的转运蛋白基因并产生无效突变体。我们的模型预测， 3 - 1，6葡聚糖的合成，但不是3 - 1，3葡聚糖的合成，将被阻止， 无效突变体第二个独立的策略是直接确定 β-1，6葡聚糖链起始和延伸的亚细胞位点。 这将通过体内放射性标记实验结合 用细胞分离法。这项工作将通过使用突变体来促进 β-1，6葡聚糖合成（KRE）和分泌（SEC）缺陷。最终 方法包括识别和表征酶， 负责合成β-1，6葡聚糖。从这些信息中获得的信息 这些研究将提供重要的新知识， 真菌细胞壁组装。

DESCRIPTION: (Verbatim from the applicant's description) In yeast and other fungi, cell shape, growth, and cell division depend on the coordinated synthesis and degradation of cell wall components. A quantitatively minor but functionally critical component of the yeast cell wall is the polymer beta-1,6 glucan. This polysaccharide is covalently cross-linked to other cell wall components, such as chitin, 3'-1,3 glucan and mannoproteins. These cross-links stabilize and organize the cell wall. The long-term goal of this project is to investigate the mechanisms by which beta-1,6 glucan is synthesized and associated with other cell wall components. We hypothesize that key aspects of beta-1,6 synthesis differ from those of the more abundant 3'-1,3 glucan polymer. Specifically, the proposed work will examine the hypothesis that beta-1,6 glucan synthesis is initiated in the lumen of the endoplasmic reticulum. Chain elongation and branching occurs in the Golgi apparatus, where the assembled polymers are packaged into secretory vesicles for delivery to the periplasmic space and assembly into the cell wall. In previous work we demonstrated the transport of UDP-glucose, the sugar donor for polymer assembly, into the lumen of the endoplasmic reticulum in Saccharomyces cerevisiae. In order to test our hypothesis we will identify the UDP-glucose transporter gene in yeast and generate a null mutant. Our model predicts that '3-1,6 glucan synthesis, but not 3'-1,3 glucan synthesis, will be prevented in the null mutant. A second, independent, strategy is to determine directly the subcellular sites in which beta-1,6 glucan chains are initiated and extended. This will be accomplished by in vivo radiolabeling experiments in combination with cell fractionation. This work will be facilitated by the use of mutants defective in beta-1,6 glucan synthesis (kre) and secretion (sec). The final approach consists of identifying and characterizing the enzymes that are responsible for synthesis of '3-1,6 glucan. The information derived from these studies will provide important new knowledge on the molecular mechanism of fungal cell wall assembly.