Structure & Function of Human Hexacoordinate Hemoglobins

结构

• 批准号: 6769384
• 负责人: MARK S HARGROVE
• 金额: $ 21.71万
• 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/6769384
• 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)：最近在人类中发现了两种六配位血红蛋白(HxHbs)。脑红蛋白是第一个被发现的人类hxHb，并且定位于大脑。我们已经确定了第二种人类hxHb，目前被称为组红蛋白(组Hb)，几乎在所有组织中都能发现。HxHbs是一类蛋白质，广泛存在于动物、植物和光合作用微生物等生物体中。命名法“hxHb”表示具有类似于细胞色素b5的配体结合位置的分子内配位的血红蛋白。尽管存在这种障碍(细胞色素b5不与气态配体结合)，hxHbs与配体的结合是可逆的，而且亲和力明显很高。NeuroHb被认为在低氧期间对细胞存活起作用，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(S)，并了解它们的功能是如何由蛋白质结构决定的。该方案的目的是测量人hxHbs对包括02和一氧化氮(NO)在内的配体的亲和力，识别这些蛋白质的基本调控元件，并评估它们在体外和体内清除NO的能力。我们的中心假设是，神经Hb和组织Hb是高亲和力的HBs，它们使用可逆的六配位和蛋白质构象变化来调节配体结合。我们进一步认为，神经Hb对神经组织中的NO具有清除作用。我们目标的基本原理是，对这些蛋白质与其生物配体的反应的基础检查对于确定它们潜在的生理作用至关重要。 为了验证我们的假设，本文提出了四个具体目标。1)02、CO、NO和CN-与神经Hb的结合特性。2)阐明人神经Hb的配体结合结构和机制。3)检测神经Hb的NO双氧合活性，并评价其生理意义。4)组织Hb的结构和生物物理特性，以及其作为NO双加氧酶的功能。 血红蛋白和一氧化氮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。我们的工作至关重要，因为hxHbs被证明是生物上无处不在的分子，我们必须评估它们参与人类体内非稳态的可能性。此外，我们对神经Hb和组织Hb的实验将开发出适用于所有hxHb的一般原理。