Clinical Proteomics Unit, Division of Molecular Medicine, St. John's Research Institute, St. John's National Academy of Health Sciences, 100ft Road, Koramangala, Bangalore, 560034, India.
J Am Soc Mass Spectrom. 2018 Oct;29(10):2048-2058. doi: 10.1007/s13361-018-2011-1. Epub 2018 Jul 2.
Besides multiple life-threatening diseases like lung cancer and cardiovascular disease, cigarette smoking is known to produce hypoxia, a state of inadequate oxygen supply to tissues. Hypoxia plays a pivotal role in the development of chronic obstructive pulmonary disease. Smoking during pregnancy imposes risk for the unborn child. In addition to carbon monoxide, conjugation of para-benzoquinone (pBQ), derived from cigarette smoke, with human hemoglobin (HbA) was also reported to contribute in hypoxia. In fact, conjugation of pBQ is more alarming than carbon monoxide as it is an irreversible covalent modification. In the present study, the functional assay of Hb-pBQ, performed through oxygen equilibrium curve, showed a significant decrease in both P and cooperativity. However, the structural changes associated with the observed functional perturbation of the hemoglobin conjugate (Hb-pBQ) are unknown to date. Enhanced sensitivity and high resolution of nano-ESI mass spectrometry platform have enabled to investigate the native structure of oligomers of hemoglobin in a single scan. The structural integrity of Hb-pBQ measured through the dissociation equilibrium constants (K) indicated that compared to HbA, K of tetramer-dimer and dimer-monomer equilibria were increased by 4.98- and 64.3-folds, respectively. Using isotope exchange mass spectrometry, we observed perturbations in the inter-subunit interactions of deoxy and oxy states of Hb-pBQ. However, the three-dimensional architecture of Hb-pBQ, monitored through collision cross-sectional area, did not show any change. We propose that the significant destabilization of the functionally active structure of hemoglobin upon conjugation with pBQ results in tighter oxygen binding that leads to hypoxia. Graphical Abstract ᅟ.
除了肺癌和心血管疾病等多种危及生命的疾病外，吸烟还会导致缺氧，即组织供氧不足。缺氧在慢性阻塞性肺疾病的发展中起着关键作用。怀孕期间吸烟会对未出生的孩子造成风险。除了一氧化碳外，香烟烟雾中产生的对苯醌（pBQ）与人体血红蛋白（HbA）的结合也被报道会导致缺氧。事实上，pBQ 的结合比一氧化碳更令人担忧，因为它是一种不可逆的共价修饰。在本研究中，通过氧平衡曲线进行的 Hb-pBQ 功能测定表明，P 和协同性都显著降低。然而，与血红蛋白结合物（Hb-pBQ）观察到的功能紊乱相关的结构变化目前尚不清楚。纳米电喷雾质谱平台的高灵敏度和高分辨率使我们能够在单次扫描中研究血红蛋白低聚物的天然结构。通过解离平衡常数（K）测量的 Hb-pBQ 结构完整性表明，与 HbA 相比，四聚体-二聚体和二聚体-单体平衡的 K 值分别增加了 4.98 倍和 64.3 倍。通过同位素交换质谱，我们观察到脱氧和氧合状态下 Hb-pBQ 亚基间相互作用的扰动。然而，通过碰撞截面面积监测的 Hb-pBQ 的三维结构没有发生任何变化。我们提出，pBQ 与血红蛋白结合导致血红蛋白功能活性结构的显著失稳，从而导致缺氧。
