Structure and Function of Fission Yeast Signal Recognition Particle

信号识别颗粒（SRP）是一种核糖核蛋白，由 6个蛋白质亚基和1个7SL RNA分子，是第一元件 识别蛋白质的专门机制， 通过分泌途径从真核细胞输出。 基于in 在体外实验中，已经假设，在出现 信号序列的核糖体，SRP结合和逮捕翻译。 当复合物到达内质网（ER）膜时，SRP 与特定受体相互作用，解离，并翻译 蛋白质恢复伴随着载体易位进入ER 流明 通过利用裂变酵母的独特优势 粟酒裂殖酵母，我们将从基因和生化角度 分泌蛋白靶向，首先关注必需的7SL SRP的组成部分。 克隆基因的随机诱变， 转化和筛选条件性或部分分泌性 缺陷将识别对细胞中的功能至关重要的核苷酸， vivo. 保守的序列和结构将由 比较来自不同生物体的7SL同源物， 其作用模式的具体模型，将由现场进行测试- 定向诱变的S.粟酒基因 抑制器选择将 鉴定与7SL RNA相互作用的其他组分， 裂殖酵母SRP蛋白;其他可能的靶点包括SRP 受体和核糖体蛋白。 与遗传同时发生 实验中，将开发一个同源的体外系统来研究SRP 功能;它也将是有用的生化表征 突变体的缺陷 这些研究将提供深入了解 细胞对蛋白质进行排序的机制，其显着特征是 在裂变酵母和人类之间是保守的。

Signal recognition particle (SRP), a ribonucleoprotein composed of six protein subunits and one molecule of 7SL RNA, is the first element of the specialized machinery which recognizes proteins destined for export from eukaryotic cells via the secretory pathway. Based on in vitro experiments, it has been postulated that, upon emergence of the signal sequence from the ribosome, SRP binds and arrests translation. When the complex arrives at the endoplasmic reticulum (ER) membrane, SRP interacts with a specific receptor, dissociates, and translation of the protein resumes accompanied by vectorial translocation into the ER lumen. By exploiting the unique advantages of the fission yeast Schizosaccharomyces pombe, we will genetically and biochemically dissect secretory protein targeting, focusing first on the essential 7SL component of SRP. Random mutagenesis of the cloned gene followed by transformation and screening for conditional or partial secretory defects will identify nucleotides which are critical for function in vivo. Conserved sequences and structures will be determined by comparison of 7SL homologs from divergent organisms, allowing generation of specific models for its mode of action which will be tested by site- directed mutagenesis of the S. pombe gene. Suppressor selection will identify other components which interact with 7SL RNA, minimally the fission yeast SRP proteins; other likely targets include the SRP receptor and ribosomal proteins. Concurrent with the genetic experiments, a homologous in vitro system will be developed to study SRP function; it will also be useful for biochemically characterizing defects in the mutants. These studies will provide insight into the mechanism by which cell sort proteins, the salient features of which are conserved between fission yeast and humans.