Structure & Function of Human Hexacoordinate Hemoglobins

结构

• 批准号: 6612200
• 负责人: MARK S HARGROVE
• 金额: $ 23.1万
• 依托单位: IOWA STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6612200
• 关键词: X ray crystallography; binding sites; conformation; electron spin resonance spectroscopy; ferriheme; hemoglobin; hypoxia; ligands; nitric oxide; oxidation reduction reaction; oxygen; protein binding; protein protein interaction; protein structure function; site directed mutagenesis

DESCRIPTION (provided by applicant): Two hexacoordinate hemoglobins (hxHbs) have very recently been identified in humans. Neuroglobin (neuroHb) was the first human hxHb discovered, and is localized in the brain. We have identified a second human hxHb that is currently referred to as histoglobin (histoHb), and is found in nearly all tissues. HxHbs are a class of proteins found in a wide array of organisms including animals, plants, and photosynthetic microorganisms. The nomenclature "hxHb" denotes a hemoglobin with intramolecular coordination of the ligand binding site similar to cytochrome b5. In spite of this obstruction (cytochrom b5 does not bind gaseous ligands), hxHbs bind ligands reversibly and with apparently high affinities. NeuroHb is thought to play a role in cell survival during hypoxia, but no physiological roles have yet been established with confidence for these proteins. Our long range goal is to deduce the physiological role(s) of human hxHbs, and to understand how their function is dictated by protein structure. The objective of this proposal is to measure the affinities of human hxHbs for ligands including 02 and nitric oxide (NO), to identify basic regulatory elements of these proteins, and to evaluate their capacity to scavenge NO both in vitro and in vivo. Our central hypothesis is that neuroHb and histoHb are high affinity Hbs that use reversible hexacoordination and protein conformational changes to regulate ligand binding. We further suggest that neuroHb serves to scavenge NO in neural tissues. The rationale underlying our objective is that fundamental examination of the reactions of these proteins with their biological ligands is crucial in ascertaining their potential physiological roles. Four specific aims are proposed to test our hypotheses. 1) Characterization of 02, CO, NO, and CN- binding to neuroHb. 2) Elucidation of the structure and mechanism of ligand binding for human neuroHb. 3) Examination of the NO dioxygenation activity of neuroHb, and evaluation of its physiological relevance. 4) Structural and biophysical characterization of histoHb, and its ability to function as an NO dioxygenase. The study of both hemoglobins and NO have been important topics in medical research for some time. But a large body of recent work has made it clear that we are only beginning to realize the physiological significance of their interactions with one another. Our work is critical as hxHbs are proving to be biologically ubiquitous molecules, and it is imperative that we assess their potential involvement in NO homeostasis in humans. Additionally, our experiments with neuroHb and histoHb will develop general principles that will be applicable to all hxHb.

描述（由申请人提供）：最近在人体中发现了两种六配位血红蛋白（hxHbs）。脑红蛋白（NeuroHb）是第一个发现的人类hxHb，定位于大脑。我们已经确定了第二个人类hxHb，目前被称为组织血红蛋白（histoHb），并发现在几乎所有的组织。HxHbs是一类在包括动物、植物和光合微生物在内的广泛生物体中发现的蛋白质。命名法“hxHb”表示具有类似于细胞色素b5的配体结合位点的分子内配位的血红蛋白。尽管有这种障碍（细胞色素b5不结合气态配体），hxHbs可逆地结合配体，并具有明显的高亲和力。NeuroHb被认为在缺氧期间的细胞存活中起作用，但这些蛋白质的生理作用尚未确定。 我们的长期目标是推断人类hxHbs的生理作用，并了解它们的功能如何由蛋白质结构决定。该提议的目的是测量人hxHbs对包括O2和一氧化氮（NO）的配体的亲和力，以鉴定这些蛋白质的基本调节元件，并评估它们在体外和体内抑制NO的能力。我们的中心假设是，neuroHb和histoHb是高亲和力的血红蛋白，使用可逆的六配位和蛋白质构象的变化来调节配体结合。我们进一步表明，neuroHb服务于在神经组织中的NO。我们的目标的基本原理是，这些蛋白质与其生物配体的反应的基本检查是至关重要的，在确定其潜在的生理作用。 提出了四个具体目标来检验我们的假设。1)02、C 0、N 0和CN-与神经Hb结合的表征。2)人神经血红蛋白的结构和配体结合机制的阐明。3)检测neuroHb的NO双加氧活性，并评价其生理相关性。4)histoHb的结构和生物物理特性，以及其作为NO双加氧酶的功能。 一段时间以来，血红蛋白和NO的研究一直是医学研究的重要课题。但最近的大量研究表明，我们才刚刚开始意识到它们相互作用的生理意义。我们的工作是至关重要的，因为hxHbs被证明是生物学上普遍存在的分子，我们必须评估它们在人类NO稳态中的潜在参与。此外，我们的neuroHb和histoHb实验将开发适用于所有hxHb的一般原则。