Interplay between the Signal Recognition Particle and Trigger Factor at the Ribos

描述（由申请人提供）：细胞竭尽全力确保蛋白质的适当生物发生。在翻译过程中，核糖体与修饰酶、伴侣和靶向复合物等多种因子结合，以保证最终产物的活性、正确折叠并正确定位到适当的细胞位置。没有这些因素，细胞将充满无活性、错误折叠、聚集和/或错误分配的蛋白质。这种情况会导致细胞功能失常和死亡，从而导致许多毁灭性的疾病。已经进行了许多研究来了解核糖体与这些分子机制的相互作用；然而，这些研究都没有关注核糖体如何处理和与多个复合体通信。在本文中，我们建议研究翻译核糖体与确保正常生物发生的两个核糖体相关因子：信号识别粒子（SRP）和触发因子（TF）的相互作用。SRP是一种普遍保守的靶向机制，负责将膜和分泌蛋白传递到质膜或内质网。另一方面，TF是一种细菌伴侣，有助于细胞质和质周蛋白的折叠。SRP和TF已被证明同时与核糖体结合，然而，新出现的蛋白质如何进入SRP途径或TF途径的分子基础尚不清楚。我建议(1)测试SRP和TF是否以及如何竞争与核糖体新生链复合物（rna）的结合；(2)确定SRP受体的募集是否有助于排除TF；(3)测试新生链的进一步延伸是否有利于TF相互作用并将SRP从核糖体中移除。总的来说，这些拟议的实验结果将提供核糖体如何实现“决策”的全面和定量的分子机制，并将作为理解其他核糖体相关分子机制相互作用的重要框架。

DESCRIPTION (provided by applicant): A cell goes to great lengths to ensure the proper biogenesis of proteins. During translation, the ribosome associates with multiple factors such as modification enzymes, chaperones and targeting complexes to guarantee that the final product is active, properly folded and correctly localized to the appropriate cellular location. Without these factors, the cell will be filled inactive, misfolded, aggregated and/or incorrectly allocated proteins. Such a scenario can result in the cell's malfunction and death, leading to many devastating diseases. Many studies have been carried out to understand the interaction of the ribosome with these molecular machineries; however, none of these studies look at how the ribosome handles and communicates with multiple complexes. In this proposal, we propose to study the interaction of a translating ribosome with two ribosome-associated factors that ensure proper biogenesis: the signal recognition particle (SRP) and the trigger factor (TF). SRP is a universally conserved targeting machinery and is responsible for delivering membrane and secretory proteins to the plasma membrane or to the endoplasmic reticulum. On the other hand, TF is a bacterial chaperone that aids in the folding of cytosolic and periplasmic proteins. SRP and TF have been shown to simultaneously bind to the ribosome, however, the molecular basis of how newly emerging proteins is funneled to either the SRP pathway or the TF pathway remains unclear. I propose to (1) test whether and how SRP and TF compete for binding to ribosome nascent chain complexes (RNCs); (2) determine if the recruitment of the SRP receptor helps exclude TF; and (3) test whether further elongation of the nascent chain favors TF interaction and removes SRP from the ribosome. Overall, the results of these proposed experiments will provide a comprehensive and quantitative molecular mechanism of how 'decision-making' is achieved by the ribosome and will serve as an important framework to understand the interplay of other ribosome- associated molecular machineries. PUBLIC HEALTH RELEVANCE: Upon translation of the protein, the ribosome interacts with multiple cellular factors to ensure that its final product is active, properly folded and correctly localized in the cell. In this proposal, we propose to study the interplay of two ribosome-associated complexes: the signal recognition particle and trigger factor. Results from the proposed experiments will help further our understanding of how the ribosome handles these molecular machineries and determine important concepts of how protein biogenesis is achieved.