Cloning of Tomato Fruit Polygalacturonase (PG) Converter Protein : Analysis of PG Isozyme Function

番茄果实果胶水解活性的研究 多聚半乳糖醛酸酶（PG）在 由于存在三种密切相关的同种型而成熟， PG1、PG2A和PG2B。 Pg2亚型由单个 催化PG多肽，而PG 1是由以下组成的异二聚体： 一个PG2多肽与辅助多肽紧密结合 糖蛋白，PG转换器。 每种亚型的参与 在果胶降解和果实成熟的其它方面仍然存在 不清楚 植物中的PG亚型水平似乎是由 通过转换蛋白的水平。 以提高我们 了解生物合成、组装和生物活性 细胞壁酶如PG的水平， 将通过改变其水平在体内操纵同种型 转基因野生型植物中的转化蛋白。 完成 该转化蛋白将被纯化、克隆， 野生型果实成熟过程中的结构和表达进行了研究。 转换蛋白水平将通过表达一种 在转基因中正义和反义方向的转换器cDNA 野生型番茄植株可能导致 只有PG1或PG2。 这些研究将增加我们对 单个PG亚型对多糖苷酸降解的影响， 与果实成熟相关的其他生理参数。 植物分泌多种酶和结构蛋白 细胞进入细胞壁。 这些蛋白质的活性是 对于正常生长和发育以及专门的 功能，如果实成熟和植物防御。 一个重要 问题是，这些重要蛋白质的活性是如何被 当它们从细胞中分泌出来时， 与调节细胞质中的 内切酶 该提案描述了一种有趣的方法， 研究胞外酶的加工和功能， 多聚半乳糖醛酸酶，降解细胞壁中的多聚糖醛酸 在水果成熟期间。 //

The activity of the tomato the tomato fruit pectin-hydrolyzing enzyme polygalacturonase (PG) increases dramatically during ripening due to the presence of three closely related isoforms, PG1, PG2A and PG2B. The Pg2 isoforms are composed of single catalytic PG polypeptides while PG1 is a heterodimer consisting of one PG2 polypeptide in tight association with an ancillary glycoprotein, the PG converter. The involvement of each isoform in pectin degradation and other aspects of fruit ripening remain unclear. The PG isoform levels in planta appear to be determined by the level of converter protein. In order to increase our understanding of the biosynthesis, assembly and biological activity of cell wall enzymes such as PG, the levels of individual PG isoforms will be manipulated in vivo by altering the levels of converter protein in transgenic wild-type plants. To accomplish this the converter protein will be purified, cloned and its structure and expression during wild-type fruit ripening studied. Converter protein levels will be manipulated by expressing a converter cDNA in sense and antisense orientations in transgenic wild-type tomato plants presumably resulting in accumulation of only PG1 or PG2. These studies will increase our knowledge of the effect of individual PG isoforms on polyuronide degradation and other physiological parameters associated with fruit ripening. Several enzymes and structural proteins are secreted from plant cells into the cell wall. The activities of these proteins are essential for normal growth and development as well as specialized functions such as fruit ripening and plant defense. An important question is how the activities of such important proteins is controlled when they are secreted from the cell and not subject to the normal mechanisms associated with the regulation of cytoplasmic enzymes. This proposal describes an interesting approach to studying the processing and function of an extracellular enzyme, polygalacturonase, which degrades polyuronides in the cell wall during fruit ripening. //