Mechanisms of Energy Conservation in Bifurcating Electron Transfer Flavoproteins

就像电线将电力输送到我们房子里的每一个房间一样，细胞有专门的蛋白质携带从产生电子的反应中产生的电子流到需要它们的重要反应中。该项目针对的是一类新发现的“电子转移黄素蛋白”(ETF)，它们充当能量经纪人，通过接受中能电子对并将它们的能量集中在其中一个电子上来换取质量，从而产生一个高能电子。至关重要的是，这一生化“加速站”使细胞有可能从空气中固定氮气来产生自己的肥料，从而使粮食生产成为可能，否则粮食生产将无法实现。该项目试图了解这些ETF是如何完成这一复杂过程的。这项研究试图通过研究发生这种情况的分子(这种黄素是核黄素维生素B2的衍生物)来了解能量在两个电子之间重新分配的位置的特殊之处。这项研究还试图确定构建在蛋白质支架中的安全机制，这些机制允许在良性、无毒的蛋白质中发生这种要求苛刻的转变。因此，这项工作的目的是阐明这一过程的基本原则，以便将它们设计成人造设备和材料，以提高我们使用太阳能的能力，并提高我们使用电能的效率和通用性。黄素只是许多植物色素中的一个例子，这些色素具有强大的化学性质和灿烂的颜色。该项目的科学家们通过一系列关于植物色素、纤维和香料的研讨会和课程来分享他们对颜料的热情。在这些课程中，参与者使用天然材料创建了一个纤维艺术项目，同时学习植物颜色背后的化学原理。这门创造性的化学课程为所有参与者提供了设计实验和将科学与艺术结合的机会。最近发现，一族熟悉的蛋白质具有令人惊讶的能力，能够在从NADH获得的电子对之间重新分配能量，产生比NADH源更强的还原能力(电子转移分叉，或“分叉”)。这项研究确定了这两种黄素中的哪一种在新纯化的分叉电子转移黄素蛋白(ETF)中扮演了哪种相反的角色，然后试图了解蛋白质环境的哪些方面对每一种不同的活动(传统的电子转移与分叉)负责。光谱电化学滴定测量单个氨基酸改变氨基酸取代蛋白质中黄素还原电位(EO)的程度，光谱研究阐明黄素共价键、氢键和质子化状态的变化，描绘出活性中心在产生分叉活性中的作用。目标残基包括与固氮有关的所有ETF共有的半胱氨酸，但在其他ETF中不保守。因此，这项研究可能会揭示在抑制副作用的同时利用黄素的这种反应能力所需的蛋白质背景。这个奖项反映了NSF的法定使命，通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为是值得支持的。

Just as electrical wires carry power to every room in our houses, cells have dedicated proteins carrying a current of electrons from reactions that generate electrons to vital reactions that require them. This project addresses a newly-recognized class of 'electron transferring flavoproteins' (Etfs) that act as energy brokers, trading quantity for quality by accepting pairs of modest-energy electrons and concentrating their energy onto just one of the pair to produce one high-energy electron. Crucially, this biochemical 'step-up station' makes it possible for cells to fix nitrogen gas from air to generate their own fertilizer, making food production possible where it otherwise would not be. The project seeks to understand HOW these Etfs accomplish this complex process. The research seeks to learn what is special about the site at which energy is reallocated among the two electrons by studying the molecule on which this happens (this flavin is a derivative of the riboflavin vitamin B2). The research also seeks to identify safety mechanisms built into the protein scaffold that allow such demanding transformations to occur within a benign, non-toxic protein. Thus the work aims to articulate the underlying principles of the process, so that they can be designed into human-made devices and materials, to increase our ability to use solar power and boost the efficiency and versatility with which we use electrical energy in general. Flavins are just one example of many plant pigments that present powerful chemical properties along with glorious colors. The project scientists share their enthusiasm for pigments via a series of workshops and a course on plant pigments, fibers and fragrances in which participants create a fiber art project using natural materials while learning about the chemical principles underlying plant colors. This creative chemistry course gives all participants a chance to design experiments and integrate science and art.A long-familiar family of proteins has recently been found to have a surprising capacity to re-allocate energy among pairs of electrons acquired from NADH, yielding one with more reducing power than the NADH source (electron transfer bifurcation, or 'bifurcation'). This research establishes which of the two flavins plays which of the contrasting roles identified in the newly-purified bifurcating electron transferring flavoprotein (Etf), and then seeks to understand what aspects of the protein environment are responsible for each of the different activities (conventional electron transfer vs. bifurcation). Spectroelectrochemical titrations measure the extent to which individual amino acids change the flavin reduction potentials (Eo) in proteins bearing amino acid substitutions, and spectroscopic studies elucidate changes in flavin covalent bonding, hydrogen bonding and protonation states, mapping out the active site's role in producing bifurcating activity. Residues to be targeted include a cysteine common to all the Etfs associated with nitrogen fixation but not conserved in others. Thus the research may reveal the protein context needed in order to exploit flavins' capacity for this reactivity while suppressing side-effects. The objective is to elucidate principles underlying the versatility and efficiency of bifurcation, for implementation beyond biochemistry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.