NSF Young Investigator

一个多世纪以前，巴斯德观察到氧对细胞代谢的深刻影响。现在我们知道氧气有两个主要作用。首先，过量的氧气会产生破坏细胞关键分子的活性化合物，其次，氧气过少可能会耗尽细胞功能所必需的能量资源。虽然氧在细胞生理中起着关键作用，但细胞感知和响应环境氧浓度变化的分子机制尚不清楚。为了开始理解这是如何发生的，我将尝试确定大肠杆菌转录因子Fnr是如何被缺氧激活的。在厌氧条件下，Fnr活性的增加对大肠杆菌的存活至关重要，因为Fnr通过改变参与能量代谢的基因的表达来使细胞适应缺氧。由于Fnr水平不受氧调节，关键问题是确定调节其活性的因素。对这些因素的了解最终将使细胞氧传感途径的解剖成为可能。在目前的研究计划中，将使用生化、遗传和生理方法来了解Fnr活性是如何被调节的。具体来说，我们希望定义Fnr激活的步骤，这样我们就可以定义缺氧如何影响Fnr的构象和低聚态，然后确定调节Fnr活性的因素，从而深入了解细胞氧传感的途径。许多细胞需要氧气来生长和新陈代谢。然而，过多的氧气会杀死细胞，而过少的氧气会阻止细胞的生长。因此，一个细胞要想有效地生存和生长，就必须有一种机制，使它能够识别氧气，并保护自己免受环境中氧气浓度变化的影响。大肠杆菌是一种细菌，它有一种叫做Fnr的因子，可能与这种检测系统有关。这种因子在细胞中形成，当氧气太少，无法支持细胞生长。在缺乏氧气的情况下，该因子似乎通过阻止某些酶的形成来保护细胞，这些酶通常需要在空气中形成能量。这种作用可以节省细胞能量，直到氧气再次可用，恢复生长。将进行生物化学、遗传学和生理学实验，以确定氧气如何影响Fnr的结构以及可能参与调节其形成的其他因素。＊＊＊

9357373 Kiley More than a century ago, Pasteur observed the profound effects of oxygen on cell metabolism. It is now known that oxygen has two major effects. First, excess oxygen can create reactive compounds that damage key molecules in cells, and secondly, too little oxygen may deplete energy resources vital for cell function. Although oxygen is known to play a pivotal role in cell physiology, little is known about the molecular mechanism(s) used by cells to sense and respond to changes in environmental oxygen concentrations. To begin to understand how this occurs, I will attempt to determine how the Escherichia coli transcription factor Fnr is activated by oxygen deprivation. The increase in Fnr activity under anaerobic conditions is critical for E. coli survival, since Fnr allows cells to adapt to anoxia by altering expression of genes involved in energy metabolism. Since Fnr levels are not oxygen regulated, a key problem is to identify the factor(s) which modulate its activity. Knowledge of such a factor(s) should ultimately allow dissection of the pathway for cellular oxygen sensing. In the present research program biochemical, genetic and physiological approaches will be used to learn how Fnr activity is regulated. Specifically, we wish to define the steps in Fnr activation, so that we may define how oxygen deprivation effects Fnr's conformational and oligomeric state(s), and then identify factors that regulate Fnr activity to gain insight into the pathway of cellular oxygen sensing. %%% Many cells require oxygen to grow and to metabolism. However, too much oxygen can kill cells, and too little oxygen can stop their growth. As a result, for a cell to survive and grow efficiently, there must be mechanisms which allow it to recognize oxygen and protect itself against changing concentrations of the gas in its environment. Escherichia coli, a bacterium, has a factor called Fnr, which may be involved in this detection system. This factor is formed in cells when too little oxygen is available to support cell growth. In the absence of oxygen, the factor appears to protect the cell by stopping the formation of certain enzymes ordinarily needed to form energy in air. The effect saves cell energy until oxygen again is available and growth resumes. Experiments in biochemistry, genetics and physiology will be performed to determine how oxygen influences the structure of Fnr and what other factor(s) might be involved in regulating its formation. ***