Association of turkey erythrocyte beta‐adrenoceptors with a specific lipid component.

We have recently reported that the highly potent beta‐adrenergic affinity label [125I]bromoacetylamino cyanopindolol ([125I]BAM‐CYP) irreversibly blocks the turkey erythrocyte beta‐adrenoceptor binding site by combining with a receptor‐associated non‐protein component. In this communication, we report: lipid labelling is inhibited by beta 1‐adrenergic ligands with the potency ratio and stereospecificity characteristic for the turkey erythrocyte beta 1‐adrenoceptor; the tagged component is a glycolipid, probably a ganglioside; [125I]BAM‐CYP‐blocked receptor, after solubilization in deoxycholate, can be separated from the [125I]BAM‐CYP‐glycolipid with restoration of the binding capacity of the beta 1‐adrenoceptor protein; the tightly associated [125I]BAM‐CYP‐labelled glycolipid can be displaced by a glycolipid mixture extracted from turkey erythrocyte membranes but not by bovine brain gangliosides, when the blocked receptor is solubilized in digitonin. This is the first direct demonstration that a receptor protein is associated with a specific membrane lipid. The possibility that glycolipids play a role in receptor‐mediated signal transduction is discussed in view of these findings and in view of data from the literature.