"Collaborative Research" Chemical & Genetic Modification of Biological Iron-Sulfur Clusters: Azotobacter Vinelandii Ferredxin I

铁硫（Fe- s）蛋白含有主要由铁、S2和半胱氨酸残基组成的簇。这些蛋白质普遍存在于所有已知的生物体中，是每一个基本生物过程的核心。三种类型的团簇分别含有1、2和4个铁原子，现在已经很好地表征了，最近发现了含有3个铁原子的团簇。前三个显示出多重氧化水平。最近的研究表明，电子传递并不是这些蛋白质的唯一功能。现在非常清楚的是，Fe-S团簇结构的多样性比以前认识到的要大，并且还在继续扩大。化学反应远比简单、可逆的单电子氧化还原行为更为广泛。这一建议的目标是确定初级序列如何决定哪种类型的簇在给定的蛋白质中起作用。为了实现这一目标，我们将深入研究A. vinelandii fereedoxin I （AVFD）中蛋白结合的3 FE和4 FE （FE - s）簇的结构和反应性。这种小蛋白质非常适合这种研究，因为它表达多种形式，并且X射线数据变得可用。因此，计划纯化和结晶三种新形式的AvFdI，对它们进行物理化学表征，通过位点定向诱变对它们进行修饰，并纯化和表征所得的铁毒素。这项工作可能对我们了解氮酶和其他含有Fe-S中心的多中心氧化还原蛋白至关重要。强烈建议以高优先级提供支持。

Iron sulfur (Fe-S) proteins contain clusters composed predominately of Fe, S2- and cysteine residues. These proteins are ubiquitous occuring in all known organisms and are central to every essential biological process. Three types of clusters containing respectively, 1, 2, and 4 Fe atoms are now well characterized and recently clusters containg three Fe atoms have been discovered. The first three exhibit multiple oxidation levels. It has recently been shown that electron transport is not the sole function of these proteins. It is now abundantly clear that the variety of Fe-S cluster structures is greater than previously recognized and continues to expand. The chemistry is far more extensive than simple, reversible one-electron redox behavior. The goal of this proposal is to ascertain how the primary sequence determines which type of cluster is functional in a given protein. To achieve this goal the structures and reactivities of protein-bound 3 FE and 4 FE (Fe-S) clusters in A. vinelandii fereedoxin I (AVFD) will be studied in depth. This small protein is ideally suited for such an investigation, as it expresses multiple forms and X- ray data is becoming available. Consequently, it is planned to purify and crystallize the three new forms of AvFdI, characterize them physico-chemically, modify them by site directed mutagenesis, and purify and characterize the resulting fereedoxins. This work may prove crucial to our quest to understand nitrogenase and other multicentered redox proteins containing Fe-S centers. Support is strongly recommended with a high priority.