SYNTHESIS AND ASSEMBLY OF EUCARYOTIC MEMBRANES

这项建议的长期目标是了解这些事件 与真核细胞合成膜成分有关， 将这些组分组装成功能膜。 我们打算达到这一点 目的利用酵母菌尿囊素降解系统转运蛋白 酿酒酵母作为模型系统。 我们的初步实验表明， 至少有四种转运系统与尿囊素途径有关： 每种用于尿囊素和尿囊酸，两种用于尿素。 后两个系统 已经被详细研究过了 一种是可诱导，可抑制， 能量依赖性低Km主动转运系统， 能量，可能与离子梯度有关，提供驱动力 用于摄取。 第二个系统是一个组成性的，不可抑制的，能量 独立的促进扩散系统。 已经分离出一些突变体， 在尿素吸收方面有缺陷。 以这项工作为起点，我们计划 （1）结构的遗传鉴定 与尿囊素途径转运系统相关的组分，（2） 尿囊素途径的生理生化特性 运输系统及其相互作用，（3）纯化和 低Km尿素通透酶的结构表征和免疫的产生 使用该蛋白质作为抗原的血清，（4）描绘相关事件 在血浆中组装低Km尿素通透酶转运系统 膜和（5）描绘的作用所发挥的液泡在 代谢物的积累及其细胞内的调节 浓度的

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.