PHEROMONE RESPONSE AND G PROTEINS IN YEAST

酵母中的α和α交配型分泌并响应于 肽信息素、α因子和α因子。 响应是 由信息素与特定受体结合而引发 在相反交配类型的细胞上。 a和的结构 α-因子受体的结构与 受体介导的脊椎动物信号转导途径 G（鸟嘌呤核苷酸结合）蛋白，包括 光转导和β-肾上腺素能反应途径。 酵母SST 2和SCG 1基因是通过 信息素应答突变（SST 2）的互补。 这些 基因编码的蛋白质可能在 两种交配类型共有的信息素反应途径。 SST 2可能在信息素脱敏中起作用 类似于抑制蛋白在脱敏中的作用， 光传导途径 SCG 1显示出高度的 与参与其他信号转导的G蛋白同源 系统. 拟议研究的目的是进一步表征 SST 2和SCG 1产物在信息素中的作用 反应途径，以测试SST 2和SCG 1的特定模型 功能，以确定该途径的其他组分，以及 为了进一步研究脊椎动物信号的相似性， 转导系统 SST 2和SCG 1的进一步分析 这一职能将涉及审查生产过剩的影响 信息素反应和交配，屏幕上的变化- 功能突变和蛋白质产物的定位， 在有无信息素的情况下 SCG 1功能将 也可以通过鸟嘌呤核苷酸结合试验进行分析， 与G蛋白相关的GT3活性和通过构建 定点突变来检测氨基酸 已经显示出影响其他功能的取代 鸟嘌呤核苷酸结合蛋白。 其他克隆， 互补SST 2可以编码信息素的其它成分 反应途径，因此将进行分析。 抑制因子 Sst 2或scg 1功能丧失和功能改变突变 将被隔离;反应途径组分的突变 应该在抑制剂中被识别出来。 最后，杂交 分析表明，有额外的酵母序列， 与SCG 1同源;将分析这些序列以鉴定 参与信息素反应的其他G蛋白 有趣的过程。

The a and alpha mating types in yeast secrete and respond to the peptide pheromones, a-factor and alpha-factor. The response is initiated by binding of pheromone to a specific receptor present on cells of the opposite mating type. The structures of the a- and alpha-factor receptors are very similar to the structures of receptors in vertebrate signal transduction pathways mediated by G (guanine nucleotide-binding) proteins, including the phototransduction and the beta-adrenergic response pathways. The yeast SST2 and SCG1 genes were isolated by complementation of a pheromone response mutation (sst2). These genes encode proteins that are likely to play important roles in the pheromone response pathway common to both mating types. SST2 is proposed to play a role in desensitization to pheromone similar to the role of arrestin in desensitization of the phototransduction pathway. SCG1 shows a high degree of homology to the G proteins involved in other signal transduction systems. The purpose of the proposed research is to further characterize the roles of the SST2 and SCG1 products in the pheromone response pathway, to test specific models for SST2 and SCG1 function, to identify additional components of this pathway, and to further investigate similarities to vertebrate signal transduction systems. Further analysis of SST2 and SCG1 function will involve examination of the effect of overproduction on pheromone response and mating, screens for change-of- function mutations, and localization of the protein products both in the absence and presence of pheromone. SCG1 function will also be analyzed by assays for guanine nucleotide-binding and GTPase activities associated with G proteins and by construction of site-directed mutations to examine the effects of amino acid substitutions that have been shown to effect the function of other guanine nucleotide-binding proteins. Additional clones that complement sst2 may encode other components of the pheromone response pathway and therefore will be analyzed. Suppressors of sst2 or scg1 loss-of-function and change-of-function mutations will be isolated; mutations in components of the response pathway should be identified among the suppressors. Finally, hybridization analysis has indicated that there are additional yeast sequences homologous to SCG1; these sequences will be analyzed to identify additional G proteins involved in pheromone response and other interesting processes.