Noncovalently and covalently bound lipid on the receptor for immunoglobulin E

We describe experiments which indicate that lipids interact with the receptor for immunoglobulin E (IgE) in several ways. Evidence for loosely bound lipid comes from observations on the special conditions that are required in order to oxidatively iodinate the alpha chain of the receptor in IgE-receptor complexes. Evidence for tightly, but still noncovalently, bound lipids comes from studies on the lipids required to inhibit dissociation of the subunits of the receptor in micellar detergent. Finally, biosynthetic studies indicate that the subunits of the receptor contain ester-linked fatty acids. The latter modification appears to take place on receptors that have already been inserted into the plasma membrane.