GENETIC ANALYSIS TO THE SIGNAL RECOGNITION PARTICLE

信号识别颗粒(SRP)是一种核糖核蛋白复合体，它 对于将出口蛋白定向到真核细胞内质中具有重要意义 网状结构。有趣的是，哺乳动物SRP组分的同源物 和SRP受体最近在整个自然界都被发现，包括在 大肠埃希菌。大肠杆菌同系物包括FFH、Fff和 FtsY基因。所有这些基因对大肠杆菌的生存都是必不可少的，而且 生化证据表明，这些基因的产物在 活着。此外，还观察到一些蛋白质出口缺陷如下 FFH和ftsY基因产物缺失。然而，目前还不清楚是如何 这些蛋白质在普遍的蛋白质输出中起作用，也不知道是否 除了蛋白质输出外，它们还在细胞过程中发挥作用。 为了确定细菌SRP FFH蛋白的细胞功能， 真核细胞SRP的54kD组分的同源物，将通过 使用遗传和生化方法相结合的方法。大肠埃希菌菌株 已经建造了允许从活跃的生长中耗尽FFH的 细胞。这些菌株将通过研究FFH的影响来表征 耗尽了各种细胞过程。最初，实验将 以确定FFH是否直接在细菌蛋白中发挥作用 出口。这项分析将包括体内和体外的使用 监控信号序列处理效率的技术和 FFH耗尽后的本地化。还将确定FFH是否 在蛋白质转位的Sec通路上的功能。 此外，FFH对细胞过程很重要的可能性 除了蛋白质出口外，还将进行测试。可能的替代活动 FFH包括在蛋白质合成和蛋白质折叠中的作用。 FFH的条件突变株也将被分离出来。这些变种人会， 同样，被定性为蛋白质出口的缺陷，以及 其他细胞过程。对FFH新突变体的研究将提供一种 以独立方式确定其基因产物的细胞功能。在……里面 此外，还将寻找其他类别的FFH突变体 为FFH的体内功能提供新的见解。 这项研究的结果将是理解SRP同源基因是如何 FFH在细菌中发挥作用。由于FFH是一种必需的蛋白质，很明显 它在关键的细胞过程中扮演着重要的角色。通过确定 这种蛋白质在体内的作用将增加我们对它的了解 所有生命共有的基本细胞过程。如果这个同源物 事实上，在蛋白质出口中的作用，那么他将获得新的见解 蛋白质如何离开细胞质。此外，由于高度的 FFH在整个自然界的保守特征，更好地理解如何 SRP在真核生物中的功能也可能产生。一个潜在的应用 这项研究的目的可能是确定抗菌剂的新靶点 并开发新技术，以更有效地出口医疗产品 重要的蛋白质。

The signal recognition particle (SRP) is a ribonucleoprotein complex that is important for targeting exported proteins to the eukaryotic endoplasmic reticulum. Interestingly, homologues to components of the mammalian SRP and SRP receptor have recently been found throughout nature, including in Escherichia coli. E. coli homologues include products of the ffh, ffs, and ftsY genes. All of these genes are essential for E. coli viability, and biochemical evidence suggests that the products of these genes interact in vivo. Furthermore, some protein export defects are observed following depletion of the ffh and ftsY gene products. However, it is unclear how these proteins function in generalized protein export, nor is it known if they function in cellular processes apart from protein export. To determine the cellular function of the bacterial SRP the Ffh protein, a homologue to a 54 kD component of the eukaryotic SRP, will be studied by using a combination of genetic and biochemical approaches. E. coli strains have been constructed that permit depletion of Ffh from actively growing cells. These strains will be characterized by studying the effects of Ffh depletion on various cellular processes. Initially, experiments will he performed to determine if Ffh functions directly in bacterial protein export. This analysis will include the use of both in vivo and in vitro techniques to monitor efficiency of signal sequence processing and localization following Ffh depletion. It will also be determined if Ffh functions on the well characterized sec pathway of protein translocation. In addition, the possibility that Ffh is important for cellular processes other than protein export will be tested. Possible alternative activities for Ffh include roles in protein synthesis and protein folding. Conditional mutants of ffh will also be isolated. These mutants will, likewise, be characterized for defects in protein export, as well as in other cellular processes. The study of new ffh mutants will provide an independent way to determine the cellular function of its gene product. In addition, other classes of ffh mutants will also be sought that should provide new insights into the in vivo function of Ffh. The outcome of this research will be to understand how the SRP homologue Ffh functions in bacteria. Since Ffh is an essential protein, it is clear that it plays an important role in key cellular processes. By determining the in vivo role of this protein we will increase our understanding of fundamental cellular processes common to all life. If this homologue indeed functions in protein export then new insights will he gained into how proteins exit the cytoplasm. Furthermore, because of the highly conserved features of Ffh throughout nature, a better understanding of how the SRP functions in eukaryotes may also result. A potential application of this research may be to identify new targets for antimicrobial agents and to develop new technologies for more efficient export of medically important proteins.