Structural and Dynamic Characterization of 2/2 Hemoglobins

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。血红蛋白最为人所知的是负责血液红色的氧气转运体。然而，蛋白质的血红蛋白超家族在生命的所有三个领域都有成员，包括细菌。人们对细菌血红蛋白知之甚少，预计许多细菌血红蛋白参与的过程不是可逆氧结合。该项目将探索细菌血红蛋白的物理化学性质，这些血红蛋白属于最近发现的超家族中2/2或“截短”的血红蛋白谱系。对血红素蛋白的反应性特别重要的是涉及辅因子的相互作用和允许氧等小配体到达中心铁的分子运动。因此，这项研究的目标是建立连接结构、动力学和反应性的牢固关系。为此，分子生物学方法和光谱方法(光学和核磁共振)的组合将被应用于一组蛋白质，这些蛋白质代表了两个在系统发育上不同的截短血红蛋白组(组I和组III)和组I中的两个不同类别。(1)在第一个特定目标中，将研究来自蓝藻聚球藻和聚球藻(组I类1)的血红蛋白的动态性质。重点将放在它们独特的双组氨酸亚铁血红素配位和亚铁血红素翻译后修饰的决定因素上。(2)第二个目的是关于发菜血红蛋白(第I类)的结构特征及其高度疏水的血红素结合部位的后果。(3)在第三个目标中，将描述肝螺杆菌(组III)血红蛋白中的血红素环境，并与其独特的配体结合性质有关。(4)最后，将设计新的核磁共振方法来探索每个蛋白质的血红素口袋中关键氢键网络的复杂细节。这四个具体目标将有助于将这些有趣的蛋白质置于血红蛋白超家族的背景下，促进对其氨基酸序列的解释，并提供对血红素化学和氧气利用的新方面的洞察。广泛影响血红蛋白超家族是一个理想的主题，可以用来说明生物化学(代谢、调节)、化学(平衡、动力学和反应)、生物学(进化)和物理(光谱)领域的基本概念。该项目为这些学科的研究生和本科生的培训以及将研究成果纳入讲座和实验室提供了极好的机会。将开发一门涵盖量子化学和光谱学的新生物物理学课程，该课程将使用血红蛋白作为重复使用的模型系统。研究结果还将以旨在提高研究生沟通技能的讲习班为基础。该系列将强调面向专业和更广泛的受众，从而促进参加讲习班的学生今后的外展活动。结果将通过出版、参加会议、在网站上张贴以及将结构数据存放在公共数据库中来传播。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Hemoglobin is best known as the oxygen transporter responsible for the red color of blood. The hemoglobin superfamily of proteins, however, has members in all three domains of life, including bacteria. Little is known about bacterial hemoglobins, and it is expected that many participate in processes other than reversible oxygen binding. The project will explore the physico-chemical properties of bacterial hemoglobins belonging to the recently discovered 2/2 or "truncated" hemoglobin lineage of the superfamily. Of particular importance to the reactivity of heme proteins are the interactions involving the cofactor and the molecular motions that allow small ligands such as oxygen to reach the central iron. The goal of the research is therefore to establish robust relationships linking structure, dynamics, and reactivity. To this end, a combination of molecular biology approaches and spectroscopic methods (optical and nuclear magnetic resonance, NMR) will be applied to a set of proteins representative of two phylogenetically distinct groups of truncated hemoglobins (Group I and Group III) and two different classes within Group I. (1) In the first specific aim, the dynamic properties of the hemoglobins from the cyanobacteria Synechococcus and Synechocystis (Group I class 1) will be studied. The focus will be on the determinants of their distinctive bis-histidine heme coordination and heme post-translational modification. (2) The second aim bears on the structural characterization of a Nostoc punctiforme hemoglobin (Group I class 2) and the consequences of its highly hydrophobic heme binding site. (3) In the third aim, the heme environment in the hemoglobin from Helicobacter hepaticus (Group III) will be described and related to its unique ligand binding properties. (4) Finally, novel NMR methods will be devised to probe the intricate details of key hydrogen-bond networks in the heme pocket of each protein. The four specific aims will help place these intriguing proteins in the context of the hemoglobin superfamily, facilitate the interpretation of their amino acid sequences, and provide insight into novel aspects of heme chemistry and oxygen utilization.Broader ImpactsThe hemoglobin superfamily is an ideal subject with which to illustrate fundamental concepts in the fields of biochemistry (metabolism, regulation), chemistry (equilibria, kinetics and reactivity), biology (evolution), and physics (spectroscopy). The project offers excellent opportunities for the training of graduate and undergraduate students in these disciplines and for inclusion of research results in lectures and laboratories. A new biophysics course covering quantum chemistry and spectroscopy will be developed that will use hemoglobins as recurring model systems. The research results will also be at the basis of workshops designed to improve the communication skills of graduate students. The series will emphasize addressing both specialized and broader audiences, thereby facilitating future outreach activities of the students participating in the workshops. Results will be disseminated through publication, participation in conferences, posting on web sites, and deposition of structural data in public databases.