Che A, Cherry R J
Department of Chemistry and Biological Chemistry, University of Essex, Colchester, England, UK.
Biophys J. 1995 May;68(5):1881-7. doi: 10.1016/S0006-3495(95)80365-6.
The effect of antibodies to glycophorin A on the rotational diffusion of band 3 in human erythrocyte membranes was investigated by transient dichrosim. Three antibodies that recognize different epitopes on the exofacial domain of glycophorin A all strongly reduce the rotational mobility of band 3. The effect is at most only weakly dependent on the distance of the epitope from the membrane surface. The degree of immobilization obtained with two of the antibodies, BRIC14 and R18, is very similar to that produced by antibodies to band 3 itself. Similar results were obtained with membranes stripped of skeletal proteins. Fab fragments and an antibody to glycophorin C had no effect on band 3 rotational mobility. These results rule out a mechanism whereby band 3 rotational immobilization results from enhanced interactions with the membrane skeleton that are mediated by a conformational change in glycophorin A. Rather, they strongly indicate that the antibodies to glycophorin A cross-link existing band 3-glycophorin A complexes that have lifetimes that are long compared with the millisecond time scale of the transient dichroism measurements.
通过瞬态二色性研究了抗血型糖蛋白A抗体对人红细胞膜中带3蛋白旋转扩散的影响。三种识别血型糖蛋白A外表面结构域不同表位的抗体均强烈降低了带3蛋白的旋转流动性。该效应至多仅微弱地依赖于表位与膜表面的距离。用两种抗体BRIC14和R18获得的固定程度与抗带3蛋白自身抗体所产生的固定程度非常相似。去除骨架蛋白的膜也得到了类似结果。Fab片段和抗血型糖蛋白C抗体对带3蛋白的旋转流动性没有影响。这些结果排除了一种机制，即带3蛋白的旋转固定是由血型糖蛋白A的构象变化介导的与膜骨架增强相互作用所致。相反，它们有力地表明，抗血型糖蛋白A抗体交联了现有的带3蛋白-血型糖蛋白A复合物，这些复合物的寿命与瞬态二色性测量的毫秒时间尺度相比很长。
