GENETIC ANALYSIS TO THE SIGNAL RECOGNITION PARTICLE

信号识别颗粒（SRP）是核糖核蛋白复合物， 对于将输出的蛋白质靶向真核细胞的内质网是重要的 网状细胞。有趣的是，与哺乳动物SRP组分的同源物 和SRP受体最近在自然界中被发现，包括在 大肠埃希菌E.大肠杆菌同源物包括FFH、FFS和 ftsY基因。所有这些基因都是大肠杆菌所必需的。大肠杆菌活力，和 生物化学证据表明，这些基因的产物相互作用， vivo.此外，观察到以下蛋白质输出缺陷： ffh和ftsY基因产物的耗竭。然而，目前还不清楚如何 这些蛋白质在广义蛋白质输出中起作用，也不知道是否 它们在除了蛋白质输出之外的细胞过程中发挥作用。 为了确定细菌SRP Ffh蛋白的细胞功能， 真核生物SRP的54 kD组分的同源物，将通过 使用遗传学和生物化学方法的组合。E.杆菌菌株 已经被构造成允许Ffh从活跃生长中耗尽 细胞这些菌株将通过研究Ffh的作用来表征。 消耗在各种细胞过程中。最初，实验将 以确定Ffh是否直接在细菌蛋白中起作用 导出.该分析将包括使用体内和体外 监测信号序列处理效率的技术， Ffh耗尽后的定位。还将确定Ffh是否 在蛋白质易位的充分表征的SEC途径上起作用。 此外，Ffh对细胞过程重要的可能性 除蛋白质外的其他物质都将被检测。可能的替代活动 包括在蛋白质合成和蛋白质折叠中的作用。 ffh的条件突变体也将被分离。这些变种人会 同样，其特征在于蛋白质输出缺陷，以及 其他细胞过程。新ffh突变体的研究将提供 独立的方式来确定其基因产物的细胞功能。在 此外，还将寻找其它类型的ffh突变体， 为Ffh的体内功能提供了新的见解。 这项研究的结果将是了解如何SRP同源 Ffh在细菌中起作用。由于Ffh是一种必需蛋白质，因此很明显 它在关键的细胞过程中起着重要的作用。通过确定 这种蛋白在体内的作用，我们将增加我们的理解， 所有生命共同的基本细胞过程。如果这个同源物 在蛋白质输出中确实起作用，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 Ffh在整个自然界中的保守特征，更好地了解如何 也可能导致真核生物中的SRP功能。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用品， 重要蛋白质

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.