Myers J N, Holowka D, Baird B
Department of Chemistry, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301.
Biochemistry. 1992 Jan 21;31(2):567-75. doi: 10.1021/bi00117a038.
Erythrosin 5'-thiosemicarbazide labeled immunoglobulin E (IgE) was used to monitor the rotational dynamics of monomeric and dimeric Fc epsilon RI receptors for IgE on rat basophilic leukemia (RBL) basophilic leukemia (RBL) cells using time-resolved phosphorescence anisotropy. Receptors were studied both on living RBL cells and on membrane vesicles derived from RBL cell plasma membrane. The un-cross-linked IgE-receptor complexes on cells and vesicles exhibit rotational correlation times that are consistent with those expected for freely rotating monomers, but a small fraction of these complexes on cells may be rotationally immobile. A comparison of the initial phosphorescence anisotropy values for erythrosin-labeled IgE-receptor complexes on cells and vesicles reveals a fast component of rotational motion that is greater on the vesicles and may be due to a site of segmental flexibility in the receptor itself. Dimers of IgE-receptor complexes formed with anti-IgE monoclonal antibodies appear to be largely immobile on cells, but they are mobile on vesicles with a 2-fold larger rotational correlation time than the monomeric complexes. The results suggest that dimeric IgE-receptor complexes undergo interactions with other membrane components on intact cells that do not occur on the membrane vesicles. The possible significance of these interactions to receptor function is discussed.
使用赤藓红5'-硫代氨基脲标记的免疫球蛋白E（IgE），通过时间分辨磷光各向异性来监测大鼠嗜碱性白血病（RBL）细胞上IgE的单体和二聚体FcεRI受体的旋转动力学。在活的RBL细胞和源自RBL细胞质膜的膜囊泡上对受体进行了研究。细胞和囊泡上未交联的IgE-受体复合物表现出的旋转相关时间与自由旋转单体预期的一致，但细胞上这些复合物的一小部分可能是旋转不动的。对细胞和囊泡上赤藓红标记的IgE-受体复合物的初始磷光各向异性值进行比较，发现旋转运动的快速成分在囊泡上更大，这可能归因于受体本身的节段灵活性位点。用抗IgE单克隆抗体形成的IgE-受体复合物二聚体在细胞上似乎基本不动，但它们在囊泡上是可移动的，其旋转相关时间比单体复合物大2倍。结果表明，二聚体IgE-受体复合物在完整细胞上与其他膜成分发生相互作用，而在膜囊泡上不会发生这种相互作用。讨论了这些相互作用对受体功能的可能意义。
