Wajcman H, Kister J, Galactéros F, Spielvogel A, Lin M J, Vidugiris G J, Hirsch R E, Friedman J M, Nagel R L
INSERM U91, Hôpital Henri Mondor, 94010 Creteil, France.
J Biol Chem. 1996 Sep 20;271(38):22990-8. doi: 10.1074/jbc.271.38.22990.
Hb Montefiore was found, in the heterozygous state, in a Puerto Rican female who had a slightly elevated total Hb level. Structural analysis revealed that Asp-alpha126 was replaced by Tyr. Hb Montefiore migrates close to HbF (at pH 8.6) and accounts for 20.3% of the hemolysate. Oxygen binding of red blood cells revealed a 40% decrease in the P50 (pH 7.4) and a low n value of 1.6 (normal: 2.6). Depletion of red blood cell 2,3-DPG did not change the results. Stripped Hb Montefiore at pH 7.2 showed an 8-fold reduction in P50 (0.6 versus 4.6 mm Hg) and very low cooperativity (n = 1.2 versus 2.9 for the control). Heterotopic effectors, as 2,3-diphosphoglycerate and inositol hexaphosphate had a normal effect and in addition, they increased cooperativity. The chloride ion effect and the Bohr effect were moderately reduced. A bezafibrate derivative (L345), known to bind alpha126, increases the P50 of HbA by 9-fold, but only by 1. 5-fold that of Hb Montefiore. Combining these functional studies with intrinsic fluorescence and Resonance Raman spectroscopy, we interpret the very low n value and the high oxygen affinity for Hb Montefiore as a result of both a destabilized T state that switches to R upon ligand binding and a deoxy T state that binds ligands with higher affinity than that of deoxy HbA. Hb Montefiore still binds ligands cooperatively, but the difference in ligand binding properties of the two quaternary states has been drastically reduced.
在一名总血红蛋白水平略有升高的波多黎各女性中发现了杂合状态的蒙特菲奥里血红蛋白（Hb Montefiore）。结构分析显示，天冬氨酸-α126被酪氨酸取代。Hb Montefiore在pH 8.6时迁移位置接近HbF，占溶血产物的20.3%。红细胞的氧结合显示P50（pH 7.4）降低了40%，n值较低，为1.6（正常为2.6）。红细胞2,3-二磷酸甘油酸（2,3-DPG）的耗尽并未改变结果。pH 7.2时的脱辅基Hb Montefiore显示P50降低了8倍（0.6对4.6 mmHg），协同性非常低（对照为n = 1.2对2.9）。2,3-二磷酸甘油酸和肌醇六磷酸等异位效应剂具有正常作用，此外，它们还增加了协同性。氯离子效应和波尔效应适度降低。一种已知与α126结合的苯扎贝特衍生物（L345）使HbA的P50增加了9倍，但仅使Hb Montefiore的P50增加了1.5倍。将这些功能研究与固有荧光和共振拉曼光谱相结合，我们将Hb Montefiore非常低的n值和高氧亲和力解释为，一方面是由于T态不稳定，在配体结合时转变为R态，另一方面是由于脱氧T态与配体的结合亲和力高于脱氧HbA。Hb Montefiore仍能协同结合配体，但两种四级状态的配体结合特性差异已大幅降低。
