Role of Cellulose and Protein in the Dictyostelium Spore Coat

western Dictyostelium孢子外壳含有约一半的多糖，包括纤维素和galuronan，约一半的蛋白质，包括至少7种不同的蛋白质。涂层分两阶段组装。首先，预先形成的外壳蛋白和胶凝蛋白被分泌出来，在细胞表面形成一层。大多数蛋白质在邻近的孢子之间交换，表明在分泌后组装发生在细胞外。一种蛋白质。是独特的，因为它不交换，好像它锚定或启动外套组装。在第二阶段，纤维素积累，蛋白质进一步组织。纤维素传统上被认为是结构和功能的主要决定因素。PI提出了两个假设来研究蛋白质和多糖的相对贡献。假设1认为，蛋白质在启动被毛组装过程中起着关键作用，因此缺乏SP86等必需蛋白质群，被毛的蛋白质部分将无法组装或不会附着在质膜上，并且积累的物质将无法正确定位。假设二表明，在没有纤维素的情况下，显微镜下可检测和可沉积的蛋白质假外壳仍然会形成。该提议有三个目的：1)破坏孢子外壳蛋白SP87的基因；2)分离孢子外壳蛋白SP86基因并对其进行破坏；3)破坏UDPGPP2基因，研究该基因对被毛结构的影响。孢子外壳和其他细胞外基质保护封闭的细胞免受不利环境的影响。虽然这些基质的组成部分是部分已知的，但这些部分是如何组合在一起的，它们的比例是如何调节的，以及保护是如何发生的，这些知识在很大程度上是由推测得出的。细胞性黏菌盘基钢菌的孢子外壳结构简单，可大量分离，纯度高，许多合成多糖的蛋白和酶的基因已被克隆并可被破坏，并且对其组成有很好的分析方法，是在分子水平上研究基质的一个很好的系统。被毛的结构和功能。本研究结果将提高我们对植物和真菌细胞壁组装的认识。＊＊＊

9316897 West Dictyostelium spore coats contain about one -half polysaccharide, including cellulose and galuronan, and about one half protein, including at least 7 different protein species. The coat is assembled in two phases. First, preformed coat proteins and the galuran are secreted, forming a layer at the cell surface. Most of the proteins exchange between neighboring spores, indicating that assembly occurs extracellularly after secretion. One protein. is unique in that it is not exchanged, as if it anchors or initiates coat assembly. During the second phase cellulose accumulates, and the proteins organize further. Cellulose has traditionally been considered to be the primary determinant of structure and function. The PI proposes two hypotheses to investigate the relative contribution of proteins and polysaccharides. Hypothesis I suggests that proteins play a critical role in initiating assembly of the coat so that the absence of essential groups of proteins such as SP86, the protein part of the coat will not assemble or will not be attached to the plasma membrane, and what accumulates will not be positioned correctly. Hypothesis II suggests that in the absence of cellulose, a microscopically detectable and sedimentable protein pseudocoat will still form.. The proposal has three aims: 1) To disrupt the gene for the spore coat protein SP87; 2) To isolate the gene for the spore coat protein SP86 and disrupt it; and 3) To disrupt the gene for UDPGPP2, and to investigate the effect of this gene on coat structure. %%% Spore coats and other extracellular matrices protect enclosed cells from unfavorable environments. Although the constituents of a number of these matrices is partially known, knowledge of how this parts fit together, how their proportions are regulated, and how protection occurs is largely derived by speculation. The spore coat of the cellular slime mold Dictyostelium is a good system to study matrices at a molecular level, becaus e it is simple it can be isolated in bulk and in high purity, the genes for a number of its proteins and enzymes for polysaccharide synthesis have been cloned and can be disrupted, and good assays exist for the composition. structure and function of the coat. The results of this investigation will enhance our knowledge about the assembly of walls in plant and fungal cells. ***