BIOSYNTHESIS OF YEAST CELL WALL BETA 1,6 GLUCAN POLYMERS

描述：(逐字摘自申请者的描述)酵母和其他 真菌、细胞形态、生长和细胞分裂依赖于协调 细胞壁成分的合成和降解。在数量上很小，但 酵母细胞壁的功能关键成分是聚合物β-1，6 葡聚糖。这种多糖是与其他细胞壁共价交联的 成分，如甲壳素、3‘-1，3葡聚糖和甘露糖蛋白。这些交叉链接 稳定和组织细胞壁。这个项目的长期目标是 研究β-1，6-葡聚糖合成的机制和 与其他细胞壁成分相关联。我们假设， β-1，6的合成不同于含量更丰富的3‘-1，3葡聚糖 聚合物。具体地说，拟议的工作将检验以下假设 β-1，6-葡聚糖的合成是在内质体腔内启动的 网状结构。链的延长和分支发生在高尔基体中，其中 组装好的聚合物被包装成分泌囊以便输送到 周质空间和组装进入细胞壁。在以前的工作中，我们 证明了UDP-葡萄糖的转运，它是聚合物的糖供体 在酵母中组装到内质网的管腔中 酿酒。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，并产生一个零突变体。我们的模型预测 ‘3-1，6葡聚糖合成，而不是3’-1，3葡聚糖合成将被阻止。 零突变体。第二个独立的战略是直接确定 启动和延伸β-1，6葡聚糖链的亚细胞部位。 这将通过体内放射性标记实验相结合来完成 对细胞进行分级。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。决赛 方法包括识别和表征符合以下条件的酶 负责合成‘3-1，6-葡聚糖。从这些信息得出的信息 研究将提供重要的新知识的分子机制。 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.