Spectroscopic and Mechanistic Studies of Heme Enzymes

描述（由申请人提供）：紫外可见和近红外磁性圆二色性（MCD）光谱和快速扫描停流光谱将用于研究血红素铁酶和相关系统。MCD与共振拉曼光谱一起沿着，将用于研究由胺、羧酸盐或酚盐配体连接的肌红蛋白的H93 G空腔突变体。 额外的MCD研究将包括血红素蛋白maquettes和转录因子NPAS2。腔突变体和血红素蛋白maquettes的研究将扩大我们的MCD光谱的数据库结构定义的血红素系统，然后我们将适用于结构不明的血红素铁系统，如NPAS2。 轴向配体的鉴定可以深入了解血红素酶的机制。 NPAS2蛋白结合两个血红素PAS结构域，这两个结构域似乎调节转录因子的活性。 停流研究将探讨氧化还原作用的四氢生物蝶呤辅因子的催化一氧化氮合酶（NOS）进行单，双混合实验与六种不同的蝶呤和三种不同的基板。 研究NOS的催化作用将有助于更好地理解NOS催化作用的信号产物一氧化氮气体（NO）的生物合成和调节。

DESCRIPTION (provided by applicant): UV-Visible and near infrared magnetic circular dichroism (MCD) spectroscopy and rapid scan stopped flow spectroscopy will be used to study heme iron enzymes and related systems. MCD, along with resonance Raman spectroscopy, will be used to study the H93G cavity mutant of myoglobin ligated by amine, carboxylate or phenolate ligands. Additional MCD studies will include heme protein maquettes and the transcription factor NPAS2. Studies of the cavity mutant and the heme protein maquettes will expand our data base of MCD spectra for structurally defined heme systems, which we will then apply to structurally uncharacterized heme iron systems such as NPAS2. Identification of axial ligands can give insight into heme enzyme mechanisms. The NPAS2 protein binds two heme PAS domains that appear to regulate the activity of the transcription factor. Stopped flow studies will explore the redox role of the tetrahydrobiopterin cofactor in the catalysis of nitric oxide synthase (NOS) by conducting single and double mixing experiments with six different pterins and three different substrates. Studying NOS catalysis will allow for a better understanding of the biosynthesis and regulation of nitric oxide gas (NO), the signaling product of NOS catalysis.