Cho M R, Eber S W, Liu S C, Lux S E, Golan D E
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Biochemistry. 1998 Dec 22;37(51):17828-35. doi: 10.1021/bi981825c.
Ankyrin mutations and combined spectrin and ankyrin deficiency are prominent features of red blood cells (RBCs) in patients with hereditary spherocytosis (HS). Band 3 is the most abundant integral protein in the human RBC membrane. Previous studies have shown that the lateral mobility, but not the rotational mobility, of band 3 is increased in RBCs from patients with severe autosomal recessive HS and selective spectrin deficiency. These observations are consistent with the steric hindrance model of lateral mobility restriction. Here we use the fluorescence photobleaching recovery and polarized fluorescence depletion techniques to measure the lateral and rotational mobility of band 3 in intact RBCs from six patients with HS, ankyrin mutations, and combined spectrin and ankyrin deficiency. As predicted by the steric hindrance model, the lateral diffusion rate of band 3 is greater in spectrin- and ankyrin-deficient RBCs than in control cells, and the magnitude of the increase correlates with the degree of spectrin deficiency. Unlike RBCs from patients with HS and selective spectrin deficiency, however, HS RBCs with ankyrin mutations exhibit a marked increase in band 3 rotational diffusion. The magnitude of the increase correlates inversely with the ankyrin/band 3 ratio and with the fraction of band 3 retained in the membrane skeleton following detergent extraction. These data suggest that ankyrin deficiency relaxes rotational constraints on the major (slowly rotating) population of band 3 molecules. Increases in band 3 rotation could be due to release of band 3 from low-affinity binding sites on ankyrin.
锚蛋白突变以及血影蛋白和锚蛋白联合缺乏是遗传性球形红细胞增多症（HS）患者红细胞（RBC）的显著特征。带3是人类红细胞膜中最丰富的整合蛋白。先前的研究表明，在患有严重常染色体隐性HS和选择性血影蛋白缺乏症的患者的红细胞中，带3的侧向迁移率增加，但旋转迁移率未增加。这些观察结果与侧向迁移限制的空间位阻模型一致。在这里，我们使用荧光漂白恢复和偏振荧光耗尽技术来测量来自六名患有HS、锚蛋白突变以及血影蛋白和锚蛋白联合缺乏症的患者的完整红细胞中带3的侧向和旋转迁移率。正如空间位阻模型所预测的，带3在血影蛋白和锚蛋白缺乏的红细胞中的侧向扩散速率比对照细胞中的更大，并且增加的幅度与血影蛋白缺乏的程度相关。然而，与患有HS和选择性血影蛋白缺乏症的患者的红细胞不同，具有锚蛋白突变的HS红细胞在带3旋转扩散方面表现出显著增加。增加的幅度与锚蛋白/带3比率以及去污剂提取后保留在膜骨架中的带3部分呈负相关。这些数据表明，锚蛋白缺乏减轻了对带3分子主要（缓慢旋转）群体的旋转限制。带3旋转的增加可能是由于带3从锚蛋白上的低亲和力结合位点释放所致。
