Reconstitution of the receptor for immunoglobulin E into liposomes. Reincorporation of purified receptors.

Mast cells and related cells have on their surface receptors that bind immunoglobulin E (IgE) with high affinity and which, when aggregated, trigger exocytosis. We recently demonstrated that when these receptors are solubilized with mild detergents, their subunits dissociate unless an appropriate lipid:detergent ratio is maintained. The conditions required to maintain the receptors' integrity appeared to parallel those previously determined as necessary to obtain adequate incorporation of unpurified IgE-receptor complexes from detergent extracts into liposomes. We now show that purified IgE-receptor complexes having the full complement of subunits become preferentially inserted into liposomes. If the receptor subunits are chemically cross-linked to each other, at least some of such receptors can be incorporated, even though lipid is omitted during their purification. The findings suggest that the IgE-binding alpha subunit of the receptor is anchored to the bilayer by means of one or both of the other subunits.