Familial secondary erythrocytosis due to increased oxygen affinity is caused by destabilization of the T state of hemoglobin Brigham (ýýýýýýýýýý(Pro100Leu)).
Familial secondary erythrocytosis due to increased oxygen affinity is caused by destabilization of the T state of hemoglobin Brigham (ýýýýýýýýýý(Pro100Leu)).
复制标题
由于氧亲和力增加而导致的家族性继发性红细胞增多症是由血红蛋白 Brigham (Pro100Leu) 的 T 状态不稳定引起的。
DOI：
10.1002/pro.2130
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Alayash,AbduI
中科院分区：
文献类型：
--
作者：
Mollan,ToddL;Abraham,Bindu;Strader,MichaelBrad;Jia,Yiping;Lozier,JayN;Olson,JohnS;Alayash,AbduI
血红蛋白 Brigham（β Pro100 至 Leu）首次在家族性红细胞增多症患者中被报道。来自同一家族的受影响个体的红细胞同时含有 HbA 和 Hb Brigham，并且与正常细胞相比表现出更高的 O2 亲和力（P50= 23 mm Hg vs. 31 mmHg，pH 7.4，37°C）。测量的溶血物的 O2 亲和力对 pH 值或氯化物浓度的变化敏感，表明玻尔和氯化物效应几乎没有变化。通过非变性阳离子交换液相色谱将 Hb Brigham 与正常 HbA 分离，并通过质谱验证氨基酸取代。然后将从患者血液中分离的 Hb Brigham 的特性与在大肠杆菌中表达的重组 Hb Brigham 的特性进行比较。动力学实验表明，Hb Brigham 的高 (R) 和低 (T) 亲和力四元态下配体结合和释放的速率常数与天然血红蛋白的速率常数相似。然而，Brigham 突变降低了 T 到 R 的平衡常数 (L)，这在配体与脱氧 Hb 结合期间加速了向 R 状态的转换，使结合速率增加了大约两倍，并在配体与 HbO2 解离期间减慢了转换，使速率降低了大约两倍。这些动力学数据有助于解释 Hb Brigham 的高 O2 亲和力特征，并为 Pro100 对亚基间接触和 T 四级结构稳定的贡献的重要性提供进一步的证据。
Hemoglobin Brigham (β Pro100 to Leu) was first reported in a patient with familial erythrocytosis. Erythrocytes of an affected individual from the same family contain both HbA and Hb Brigham and exhibit elevated O2affinity compared with normal cells (P50= 23 mm Hg vs. 31 mmHg at pH 7.4 at 37°C). O2affinities measured for hemolysates were sensitive to changes in pH or chloride concentrations, indicating little change in the Bohr and Chloride effects. Hb Brigham was separated from normal HbA by nondenaturing cation exchange liquid chromatography, and the amino acid substitution was verified by mass spectrometry. The properties of Hb Brigham isolated from the patient's blood were then compared with those of recombinant Hb Brigham expressed inEscherichia coli. Kinetic experiments suggest that the rate constants for ligand binding and release in the high (R) and low (T) affinity quaternary states of Hb Brigham are similar to those of native hemoglobin. However, the Brigham mutation decreases the T to R equilibrium constant (L) which accelerates the switch to the R state during ligand binding to deoxy‐Hb, increasing the rate of association by approximately twofold, and decelerates the switch during ligand dissociation from HbO2, decreasing the rate approximately twofold. These kinetic data help explain the high O2affinity characteristics of Hb Brigham and provide further evidence for the importance of the contribution of Pro100 to intersubunit contacts and stabilization of the T quaternary structure.