STRUCTURAL STUDIES ON NITRIC OXIDE SYNTHASE

这个项目的长期目标是研究结构-功能 一氧化氮合酶(NOS)的关系。一氧化氮合酶是酶 负责将精氨酸氧化成一氧化氮(NO)。在……里面 近年来，一氧化氮被认为是一种主要的生理性物质。 参与神经、免疫和心血管的信使分子 系统。由于NO作为一种监管手段的效力和重要性 分子方面，一氧化氮合酶是一种受到严格控制的复合酶。这种酶 由一个血红素结构域组成，精氨酸的实际氧化发生在这个区域 以及FMN/FAD结构域，用于将电子从NADPH传输到 血红素域。在血红素和黄素结构域之间有一个连接子，它结合了 另一种调节分子，钙调蛋白。除了亚铁血红素、FMN和 FAD，NOS含有另一个未知功能的辅因子， 四氢生物蝶呤。序列比对清楚地表明Flavin 结构域与细胞色素P450还原酶非常相似，但血红素 结构域与其他血红素蛋白几乎没有相似之处，尽管 在功能和光谱性质上都与P450相似。我们的目标 是确定一氧化氮合酶的三种主要形式的晶体结构： 巨噬细胞诱导型或诱导型一氧化氮合酶，神经型或神经型一氧化氮合酶，内皮细胞或内皮型一氧化氮合酶。 由于最独特的特征是血红素域，而且由于血红素 领域是合理药物设计的首要目标，我们最初有 专注于明确所有三个人的血红素结构域。世界上的水晶 ENOS血红素结构域衍射至2.5A，nNOS和 获得了inos的血红素结构域。我们最初的目标是解决 ENOS血红素结构域的晶体结构。

The long range goal of this project is to study structure-function relationships in nitric oxide synthase (NOS). NOS is the enzyme responsible for the oxidation of arginine to nitric oxide (NO). In recent years nitric oxide has been recognized as a major physiological messenger molecule involved in the nervous, immune, and cardiovascular systems. Owing to the potency and importance of NO as a regulatory molecule, NOS is a complex enzyme under stringent control. The enzyme consists of a heme domain where the actual oxidation of arginine occurs and an FMN/FAD domain that serves to shuttle electrons from NADPH to the heme domain. Between the heme and flavin domains is a linker that binds another regulator molecule, calmodulin. In addition to heme, FMN, and FAD, NOS contains yet another cofactor of unknown function, tetrahydrobiopterin. Sequence alignments clearly show that the flavin domain is very similar to cytochrome P450 reductase but that the heme domain bears little resemblance to other heme proteins despite the similarity to P450 in both function and spectral properties. Our goal is to determine the crystal structure the three primary forms of NOS: macrophage inducible or iNOS, neuronal or nNOS and endothelial or eNOS. Since the most unique feature is the heme domain and since the heme domain is the primary target for rational drug design, we initially have focused on crystallizing the heme domain of all three. Crystals of the eNOS heme domain diffract to 2.5A and smaller crystals of the nNOS and iNOS heme domains have been obtained. Our initial goal will be to solve the crystal structure of the eNOS heme domain.