The molecular mechanism of post-peptidyl quality control on the ribosome

项目总结： 生物体的生长和生存依赖于其基因组的忠实和快速解码 信息转化为功能多肽序列。高精度的蛋白质合成确保错误的 多肽，它们更容易错误折叠，因此可能会产生不良的毒性后果， 不会被生产出来。蛋白质合成的整体保真度似乎受到 核糖体，这是两个亚单位的大分子机器，负责解码 信使RNA进入生命各个领域的蛋白质。在每个伸长周期中，核糖体 在解码过程中仔细选择与密码子匹配的适当的氨基酰tRNA(AA-tRNA) 中心来自一大群相互竞争的AA-tRNA。除此之外，我们最近还发现了一个 多肽键形成后发生的核糖体的质量控制机制， 有助于高保真蛋白质合成。类似于DNA和DNA享有的校对策略 RNA聚合酶和tRNA合成酶，新发现的基于核糖体的机制已经到位 以监测刚刚完成的化学步骤的质量。在伸长周期中，合并 一种错误的氨基酸被发现对随后的 反应。这种反复积累的错误导致蛋白质合成的流产终止，通过 释放因子，在正常情况下很少解码有义密码子。我们的长期目标是 我们的工作是彻底了解这一过程背后的分子机制。我们的 目前的目标是找出信号是如何通过干扰的mrna-tRNA相互作用传递的。 到解码中心，最终导致低保真蛋白质合成。我们还感兴趣的还有 在干扰的mRNA存在的情况下，释放因子的活性是如何在正义密码子上调节的- TRNA相互作用，以及负责这一活动的结构线索。这些目标是建立起来的 在突变的平移成分的背景下围绕稳态前动力学方法，以及 低分辨率构造探测技术。作为第三个目标，我们有兴趣探索以前的 释放因子3在质量控制机制中的未知作用及其在细胞活力中的作用。 最后，我们感兴趣的是发现这个系统是否存在于真核生物中，并确定其他 这一过程中可能涉及的因素(如果有的话)。

Project Summary: Organismal growth and viability is dependent on the faithful and fast decoding of its genomic information into functional peptide sequences. High-accuracy protein synthesis ensures that errant polypeptides, which are more prone to misfold and hence may have undesirable toxic consequences, are not produced. The overall fidelity of protein synthesis appears to be limited by the action of the ribosome, which is the two-subunit macromolecular machine responsible for the decoding of the messenger RNA into protein in all domains of life. During each cycle of elongation, the ribosome carefully selects the appropriate aminoacyl-tRNA (aa-tRNA) that matches the codon in the decoding center from a large-pool of competing aa-tRNAs. In addition to this, we have recently uncovered a quality control mechanism on the ribosome that takes place after peptide-bond formation, which contributes to high-fidelity protein synthesis. Akin to the proofreading strategies enjoyed by DNA and RNA polymerases and tRNA synthetases, the newly discovered ribosome-based mechanism is in place to monitor the quality of the just completed chemical step. During the elongation cycle, the incorporation of an incorrect amino acid was found to have dramatic effects on the specificity of the subsequent reaction. This iterated accumulation of errors results in the abortive termination of protein synthesis by release factors, which under normal conditions rarely decode sense codons. The long term goal of our work is to gain a thorough understanding of the molecular mechanisms underlying this process. Our immediate goal is to find out how the signal is communicated from a perturbed mRNA-tRNA interaction to the decoding center, which ultimately leads to low-fidelity protein synthesis. We are also interested in how the activity of release factors is modulated on sense codons in the presence of a perturbed mRNA- tRNA interaction, and the structural cues that are responsible for this activity. These goals are built around pre-steady state kinetics approaches in the context of mutated translation components, and low-resolution structural probing techniques. As a third goal we are interested in exploring a previously unknown role for release factor 3 in the quality control mechanism and its utility in cellular viability. Finally we are interested in finding whether this system exists in eukaryotes, and identifying other factors, if any, that might be involved during this process.