Protein kinases that phosphorylate and regulate eIF2B

蛋白质之间的相互作用调节细胞的基本功能，确保细胞能够生长并执行其任务。每个蛋白质就像机器中的一个零件，每个蛋白质都必须在正确的位置，并在正确的时间与所有其他部件一起工作，以使机器正常工作。但与大多数机器及其部件不同的是，蛋白质不断更新，移动，并可以修改以改变其功能和/或位置。许多蛋白质作为具有共同功能的蛋白质复合物的一部分一起起作用。与此相关的一组蛋白质需要在细胞中制造（或合成）所有新蛋白质。这些被称为蛋白质合成因子。通过增加或减少某些蛋白质合成因子的活性，细胞可以精确地控制在任何一个时间产生哪些新蛋白质。改变蛋白质活性的一种常见方法是在蛋白质表面的特定位置添加磷酸基团。这被称为磷酸化，由一类称为蛋白激酶的蛋白质执行。每种激酶都对特定的信号做出反应，告诉它何时行动。我们发现一种称为eIF 2B的关键蛋白质合成因子在多个位点被磷酸化，并且这种磷酸化增强了eIF 2B的活性。我们在这里提出了一系列的实验，旨在发现细胞中存在的蛋白激酶是负责每一个磷酸化，并发现每个修饰如何改变eIF 2B在细胞中的功能。在酵母细胞中有122种蛋白激酶。利用现代技术，我们将能够同时评估每一种基因在控制eIF 2B中所起的作用。eIF 2B的功能也被称为eIF 2的第二蛋白质合成因子的磷酸化抑制。已知eIF 2在一个称为ser 51的位点磷酸化，以响应不同的细胞应激。我们已经确定eIF 2B的五个部分（或亚基）中的三个都需要正确检测eIF 2是否在这个关键调控位点磷酸化。但是eIF 2B的这三个亚基究竟是如何共同作用的呢？在第二个系列的实验中，我们建议使用遗传和生物化学工具的组合来解决这个问题。这项工作将提供重要的详细的分子信息，这些重要的蛋白质的活动是如何控制磷酸化。

Interactions between proteins modulate essential cell functions ensuring that cells can grow and perform their tasks. Each protein is like a piece in a machine, each must be in the correct place and act at the correct time with all the other parts for the machine to function properly. But unlike most machines and their parts, proteins are continually renewed, move and can be modified to alter their function and/or location. Many proteins act together as parts of protein complexes with a common function. One group of proteins relevant to this proposal is required make (or synthesize) all new proteins in the cell. These are called protein synthesis factors. By increasing or reducing the activity of some of the protein synthesis factors cells can control exactly what new proteins are made at any one time. One common way to alter the activity of proteins is by the addition of phosphate groups to specific places on the surface of the protein. This is called phosphorylation and is performed by a class of proteins called protein kinases. Each kinase responds to specific signals that tell it when to act. We have found that one key protein synthesis factor called eIF2B is phosphorylated at multiple sites, and that this phosphorylation enhances the activity of eIF2B. We are proposing here a series of experiments designed to discover which of the protein kinases present in the cell is responsible for each phosphorylation and to discover how each modification alters eIF2B function in the cell. In yeast cells there are 122 protein kinases. Using modern technologies we will be able to assess the role each one plays in control of eIF2B simultaneously. eIF2B function is also inhibited by phosphorylation of a second protein synthesis factor called eIF2. eIF2 is known to be phosphorylated at a single site called ser51 in response to diverse cell stresses. We have already determined that three of the five parts (or subunits) of eIF2B are all needed to correctly detect whether or not eIF2 is phosphorylated at this key regulatory site. But how exactly do these three subunits of eIF2B act together to do this? In a second series of experiments we propose to use a combination of genetic and biochemistry tools to address this question. This work will provide important detailed molecular information on how the activities of these essential proteins are controlled by phosphorylation.