STRUCTURE/FUNCTION OF S-NITROSOHEMOGLOBIN

本项目的长期目标是提高我们对血红蛋白（Hb）的NO依赖性O2转运功能的理解。 在肺中，NO在氧合时与Hb的巯基结合（R构象），并且（S）NO基团在脱氧时在外周中释放（T结构）。 因此，从Hb释放的变构控制的NO参与外周血流量的调节。 然而，人们对NO如何影响血红蛋白的功能行为知之甚少，即，其O2结合和变构特性，或NO对肺血管张力或局部通气-灌注关系（V/Q）的影响，所有这些都严重影响组织氧合。 将测试以下假设：1）亚硝基化可以以有意义的方式影响Hb的协同性质，通过增加O2亲和力或通过促进外周中的O2释放（即，分别通过结合硫醇或血红素来增强R或T结构）。 2)S-亚硝基血红蛋白（SNO-Hb）对肺血管张力和V/Q匹配的影响依赖于PO2。 3)对SNO-Hb和亚硝基Hb的结构和功能行为的进一步了解可用于测量人体血液中的这些物质。最终，这些研究应导致更好地了解NO和蛋白质之间的功能调节相互作用，血红蛋白的呼吸功能，和肺血管张力的O2依赖性控制。 我们的研究结果也可能有影响的疾病状态，如败血症，镰状细胞性贫血，持续性肺动脉高压的新生儿，并在治疗环境中，如使用吸入NO，其中O2的输送和血红蛋白的功能被改变。

The long-term goal of this project is to improve our understanding of the NO-dependent O2 transport functions of hemoglobin (Hb). In the lung, NO binds to the thiol of Hb upon oxygenation (R conformation), and the (S)NO group is released in the periphery upon deoxygenation (T structure). Thus, allosterically-controlled NO release from Hb participates in the regulation of peripheral blood flow. However, very little is known of how NO affects the functional behavior of Hb, i.e., its O2 binding and allosteric properties, or what effect NO has on pulmonary vascular tone or regional ventilation-perfusion relationships (V/Q), all of which critically influence tissue oxygenation. The following hypotheses will be tested: 1) That nitrosylation can affect the cooperative properties of Hb in a meaningful way, either by increasing O2 affinity or by facilitating O2 release in the periphery (i.e., by reinforcing the R or T structures through binding thiols or hemes, respectively). 2) That the effects of S-nitrosohemoglobin (SNO-Hb) on pulmonary vascular tone and V/Q matching are dependent on the PO2. 3) That an improved understanding of the structure and the functional behavior of SNO-Hb and nitrosylHb can be used to make measurements of these species in human blood. Ultimately, these studies should lead to a better understanding of the function-regulating interactions between NO and protein, the respiratory functions of Hb, and the O2-dependent control of pulmonary vascular tone. Our results may also have implications in disease states such as sepsis, sickle cell anemia, and persistent pulmonary hypertension of the newborn, and in therapeutic settings such as the use of inhaled NO, where O2 delivery and Hb functions are altered.