Engineering H-NOX Domains for Therapeutic Oxygen Delivery

描述（由申请人提供）：拟议研究的目标是对临时氧载体进行生物工程改造，用作库存血液的替代品。目前，由于血液供应短缺和通过捐献血液传播的潜在感染，特别是在缺乏清洁血液供应的国家，需要血液替代品。目前正在研究的基于血红蛋白和全氟化碳的临时血液替代品，由于副作用，尚未取得重大的监管成功。该项目将专注于使用血红素一氧化氮/氧（H-NOX）蛋白家族的成员作为开发新型临时氧载体的支架。临时氧载体必须表现出在标准储存条件下的长期稳定性、在血浆中的稳定性以及相对于一氧化氮对氧的高选择性，因为一氧化氮清除导致高血压副作用。H-NOX蛋白在氧和一氧化氮之间显示配体选择性，使其成为工程的主要候选者。氨基酸突变将在血红素远端口袋中产生，以增加这些蛋白质的配体选择性，以及减缓血红素的自氧化速率。还将对H-NOX蛋白进行定向进化，以产生具有改变的配体结合特性的随机突变体库。将开发选择测定和筛选以鉴定具有所需氧结合特性的突变体。然后将进化的H-NOX进行选择测定和筛选，并且将使用共振拉曼和UV-可见光谱以及停流和激光闪光光解来测量配体结合动力学，对具有改进性质的那些突变体进行充分的光谱表征。最有希望的突变体将进行血浆相容性测试，并进行化学修饰以增加其在血浆中的稳定性。由于血液短缺和捐献血液传播疾病的风险，新型血液替代品的设计非常重要。这项研究的目标是开发一种新的血液替代品，基于已知的蛋白质支架，与目前的产品相比，它具有减少的副作用和提高的功效。

DESCRIPTION (provided by applicant): The goal of the proposed research is to bioengineer a temporary oxygen carrier for use as an alternative to banked blood. There is currently a need for blood substitutes because of shortages in the blood supply and potential infection spread through donated blood, especially in countries lacking a clean blood supply. Temporary blood substitutes currently under investigation, based on hemoglobins and perfluorocarbons, have yet to meet with significant regulatory success due to side effects. This project will focus on using members of the Heme Nitric oxide/OXygen (H-NOX) protein family as scaffolds for the development of novel temporary oxygen carriers. Temporary oxygen carriers must exhibit long-term stability under standard storage conditions, stability in plasma, and high selectivity for oxygen over nitric oxide, as nitric oxide scavenging leads to hypertensive side effects. H-NOX proteins display ligand selectivity between oxygen and nitric oxide, making them prime candidates for engineering. Amino acid mutations will be generated in the heme distal pocket to increase the ligand selectivity of these proteins, as well as slow the autooxidation rate of the heme. Directed evolution will also be performed on H-NOX proteins to generate libraries of random mutants with altered ligand binding properties. A selection assay and screen will be developed to identify mutants with the desired oxygen binding characteristics. The evolved H-NOXs will then be subjected to the selection assay and screen and those mutants with improved properties will be fully spectroscopically characterized using resonance Raman and UV-visible spectroscopy, as well as stop-flow and laser flash photolysis to measure ligand binding kinetics. The most promising mutants will be tested for plasma compatibility and chemically modified to increase their stability in plasma. The design of novel blood substitutes is very important due to blood shortages and risk of disease transmission from donated blood. The goal of this research is to develop a new blood substitute, based on a known protein scaffold, that has diminished side effects and improved efficacy as compared to current products.