BIOCHEMICAL ANALYSIS OF THE YEAST A-FACTOR RECEPTOR

多肽信息素与细胞表面受体调控的相互作用 酵母交配过程中的细胞分裂和其他生理事件 酿酒酵母。交配型单倍体细胞分泌a 多肽信息素，一种交配型细胞与之产生的因子 请回答。这种反应包括一组基因转录的变化。 细胞分裂周期停滞于G1期。据信，一个因素是 与产量细胞表面的特定受体结合，从而 产生触发生理反应的内部信号(S)。 我们的长期目标是了解信息素如何与受体结合 产生内部信号以及特定的细胞内目标 这些信号就是。因此，我们希望了解结合的途径 细胞表面的配体可以控制复杂的生理过程 比如细胞分裂。这是一个基本的生物学问题。多肽 控制细胞分裂的激素在真核生物中普遍存在。 有机体。酵母菌提供了独特的机会来结合生化和 解决这个问题的基因方法。 我们已经确定了编码a因子的基因ste3。 受体。在拟议的工作中，我们将通过直接结合分析来确定 这个基因是否真的编码了受体。使用一种基因组合 针对STE3不同部分的融合方法和抗体探针 产品，我们将确定膜上受体的拓扑结构-- 受体的哪些部分是细胞外的，以及它是否穿过 膜是初级氨基酸序列的7倍。我们会 纯化受体以确定其亚基组成并允许 详细分析了信息素的结合。例如，使用物理 技术，我们将确定受体的结构是否发生变化 当信息素被结合时。我们还将确定 当配体结合时，受体会发生变化。尤其是，受体 分子聚集在细胞表面的一个位置，是 受体-配体复合体内化？最后，我们将调查 结合的细胞内化学信号的性质 信息素对受体的作用。

Interaction between peptide pheromones and cell surface receptors controls cell division and other physiological events during mating in the yeast Saccharomyces cerevisiae. Haploid cells of the a mating type secrete a peptide pheromone, a factor, to which cells of the yield mating type respond. The response includes changes in transcription of a set of genes and arrest of the cell division cycle in G1. It is believed that a factor binds to a specific receptor on the surface of yield cells and thereby creates an internal signal(s) that triggers the physiological response. Our long-term goal is to understand how binding of pheromone to receptor generates an internal signal and what the specific intracellular targets of that signal are. Thus, we expect to understand the pathway whereby binding of ligand at the cell surface can control complex physiological processes such as cell division. This is a fundamental biological problem. Peptide hormones that control cell division are ubiquitous in eukaryotic organisms. Yeast offer the unique opportunity to combine biochemical and genetic approaches to this problem. We have identified the gene, STE3, that very likely encodes the a-factor receptor. In the proposed work we will determine by direct binding assays whether this gene indeed encodes the receptor. Using a combination of gene fusion methods and antibody probes to different portions of the STE3 product, we will determine the topology of the receptor in the membrane -- what parts of the receptor are extracellular and whether it traverses the membrane seven times as the primary amino acid sequence suggests. We will purify the receptor to determine its subunit composition and to permit detailed analysis of pheromone binding. For instance, using physical techniques, we will determine whether the structure of the receptor changes when pheromone is bound. We will also determine whether the location of the receptor changes when ligand is bound. In particular, do the receptor molecules cluster at one position on the cell surface, and are the receptor-ligand complexes internalized? Finally, we will investigate the nature of the intracellular chemical signal generated by binding of pheromone to receptor.