Protein (s) that Catalyze Extension of Plant Cell Walls

这项提案概述了对最近发现的一种蛋白质进行表征的实验，该蛋白质似乎直接参与诱导植物细胞壁的扩张。该蛋白将被提纯到足以产生兔多克隆抗体的数量。抗体将用于(I)确定蛋白质的解剖学和细胞学位置，(Ii)量化蛋白质的发育变化，以及(Iii)测试该蛋白质或同源蛋白质是否参与其他器官和其他物种的生长。纯化的蛋白质将被检测酶活性和结合特性，这可能为其延壁活性的生化机制提供线索。还将分析细胞壁，以寻找在生长素和其他生长控制剂的影响下，这种或其他蛋白质的翻译后修饰(例如，硫醇还原或蛋白质磷酸化)的证据。这一结果将检验这样一种假设，即植物细胞的扩张是由这种蛋白质在发育过程中调节的，这种蛋白质似乎是第一种被证明导致植物孤立细胞壁扩张的内源蛋白质。植物的生长主要受聚合物壁的松弛和膨胀的控制。植物细胞壁的精确分子结构和细胞壁松弛和扩张的分子机制尚不清楚。在分离的细胞壁中能够诱导这些过程的特定蛋白质的鉴定提供了强有力的证据，表明该蛋白质直接参与了这一现象。纯化和鉴定首次提供了直接研究细胞扩大的分子机制的能力。了解细胞壁松动的机制也可能为了解植物细胞壁的分子结构提供新的信息。

This proposal outlines experiments to characterize a recently identified protein that appears to be directly involved in the induction of plant cell wall expansion. The protein will be purified in quantities sufficient to raise rabbit polyclonal antibodies. The antibodies will be used (i) to identify the anatomical and cytological location of the protein, (ii) to quantify developmental changes in the protein, and (iii) to test whether this or homologous proteins are involved in growth of other organs and other species. The purified protein will be assayed for enzymatic activities and binding properties that might provide clues about the biochemical mechanism of its wall-extension activity. Cell walls will also be analyzed for evidence of post-translational modification (e.g. thiolreduction or protein phosphorylation) of this or other proteins, under the influence of auxin and other growth-control agents. The results will test the hypothesis that plant cell expansion is developmentally regulated by this protein, which appears to be the first endogenous protein shown to cause expansion of isolated plant cell walls. The growth of plants is controlled primarily by the relaxation and expansion of the polymeric wall. The precise molecular structure of the plant cell wall and the molecular mechanism of cell wall relaxation and expansion is not known. The identification of a specific protein that can induce these processes in isolated cell walls provides strong evidence that the protein is directly involved in this phenomenon. The purification and characterization provides for the first time the ability to directly investigate the molecular mechanism of cell enlargement. Understanding the mechanism of cell wall loosening may also provide new information about the molecular architecture of the plant cell wall.//