SYNTHESIS AND ASSEMBLY OF EUCARYOTIC MEMBRANES

这项建议的长期目标是了解事件 与真核细胞中合成膜成分有关，以及 将这些成分组装成功能膜。我们打算实现这一目标 目的利用酵母菌尿囊素降解系统转运蛋白 作为一个模型系统的啤酒。我们的初步实验表明，在 至少有四个转运系统与尿囊素途径有关：一个 尿囊素和尿囊酸各两个，尿素两个。后两个系统 已经进行了较为详细的研究。一种是可诱导的，可抑制的， 能量依赖、低公里的主动运输系统，由细胞质产生 能量，可能与离子梯度有关，提供驱动力 为了让人接受。第二个系统是一种结构性的、不可抑制的能量。 独立的促进扩散系统。一些突变体已经被分离出来 在尿素吸收方面存在缺陷。以这项工作为起点，我们计划 开展以下方面的工作：(1)结构基因鉴定 与尿囊素途径转运系统相关的成分，(2) 尿囊素途径的生理生化特性 运输系统及其相互作用，(3)提纯和 低KM尿素渗透酶的结构特征及其免疫产物的制备 以该蛋白为抗原的血清，(4)相关事件的描述 低KM尿素渗透酶转运系统在血浆中的组装 膜和(5)液泡在细胞膜中的作用。 代谢产物的积累及其胞内调控 浓度。

The long-range objective of this proposal is an understanding of the events associated with synthesizing membrane components in eucaryotic cells and assembling these components into a functional membrane. We intend to reach this goal using the allantoin degradative system transport proteins of Saccharomyces cerevisiae as a model system. Our preliminary experiments indicate that at least four transport systems are associated with the allantoin pathway: one each for allantoin and allantoic acid and two for urea. The latter two systems have been studied in some detail. One is an inducible, repressible, energy-dependent, low Km active transport system with cytoplasmically generated energy, perhaps in association with an ion gradient, providing the driving force for uptake. The second system is a constitutive, non-repressible, energy independent facilitated diffusion system. Some mutants have been isolated that are defective in urea uptake. Using this work as a starting point we plan to pursue the following areas: (1) Genetic identification of the structural components associated with the allantoin pathway transport systems, (2) physiological and biochemical characterization of the allantoin pathway transport systems and their interactions with one another, (3) purification and structural characterization of the low Km urea permease and production of immune sera using this protein as antigen, (4) delineation of the events associated with assembly of the low Km urea permease transport system in the plasma membrane and (5) delineation of the roles played by the vacuole in the accumulation of metabolities and regulation of their intracellular concentrations.