Shih D T, Jones R T, Shih M F, Jones M B, Koler R D, Howard J
Department of Biochemistry, School of Medicine, Oregon Health SciencesUniversity, Portland 97201.
Hemoglobin. 1987;11(5):453-64. doi: 10.3109/03630268708998005.
Hemoglobin Chico was discovered in an asymptomatic 3-year-old boy when a mild anemia was detected by a routine blood count. Affected individuals in three generations are also mildly anemic. The abnormal hemoglobin amounts to about 45% of the total. It separates from Hb A by cellulose acetate electrophoresis at pH 8.5 with a mobility similar to Hb J but does not separate in citrate agar at pH 6.2. Stability in isopropanol is slightly decreased. Its structure differs from the normal by the substitution of a threonyl residue for lysyl residue at position 66(E10) of the beta chain. The P50 of the oxygen equilibrium curve of whole blood at 37 degrees C was 38 torr compared with controls of 27 +/- 2 torr. The P50 binding studies of the isolated Hb Chico revealed a unique right shift of the equilibrium curve with an oxygen binding constant (1/P50) about half of normal. The remaining allosteric properties were essentially normal. This significant decrease in oxygen affinity appears to be due to changes in the heme region which result from the substitution of the normal beta 66 lysyl by the threonyl residue.
血红蛋白奇科是在一名无症状的3岁男孩进行血常规检查发现轻度贫血时被发现的。三代受影响个体也有轻度贫血。异常血红蛋白约占总量的45%。在pH 8.5条件下，通过醋酸纤维素电泳，它与血红蛋白A分离，迁移率与血红蛋白J相似，但在pH 6.2的柠檬酸盐琼脂中不分离。在异丙醇中的稳定性略有下降。其结构与正常结构的不同之处在于，β链第66位（E10）的赖氨酸残基被苏氨酸残基取代。37℃时全血氧平衡曲线的P50为38托，而对照组为27±2托。对分离出的血红蛋白奇科的P50结合研究显示，平衡曲线有独特的右移，氧结合常数（1/P50）约为正常的一半。其余的别构性质基本正常。氧亲和力的显著降低似乎是由于正常β66赖氨酸被苏氨酸残基取代导致血红素区域发生变化所致。
