Rotational motion of monomeric and dimeric immunoglobulin E-receptor complexes.
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.
Myers
J N
JN
Department of Chemistry, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301.
Holowka
D
D
Baird
B
B
D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D000944:Antigens, Differentiation, B-Lymphocyte / Q000737:chemistry* / Q000276:immunology; D002462:Cell Membrane / Q000737:chemistry; D004923:Erythrosine / Q000031:analogs & derivatives; D005454:Fluorescence Polarization; D015471:Leukemia, Basophilic, Acute; D046911:Macromolecular Substances; D011487:Protein Conformation; D051381:Rats; D011961:Receptors, Fc / Q000737:chemistry* / Q000276:immunology; D017455:Receptors, IgE; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte; D046911:Macromolecular Substances; D011961:Receptors, Fc; D017455:Receptors, IgE; D004923:Erythrosine