Covalent affinity labeling of the formyl peptide chemotactic receptor

The formyl peptide chemotactic receptor present on human neutrophil membranes has been covalently affinity-labeled using three different techniques. N-Formyl-Nle-Leu-Phe-Nle-125I-Tyr-Lys was cross-linked to the receptor with dimethyl suberimidate, N-formyl-Nle-Leu-Phe-Nle-125I-Tyr-Lys-Nepsilon-4-azido-2-nitrophenyl was cross-linked by photoactivation, and N-formyl-Nle-Leu-Phe-Nle-125I-Tyr-Lys-Nepsilon-bromoacetyl reacted spontaneously with the receptor. With each method, a polypeptide which migrated as a broad band on sodium dodecyl sulfate-polyacrylamide electrophoresis, with an apparent molecular weight between 55,000 and 70,000, was specifically labeled. A dose-response curve for inhibition of covalent cross-linking of the formyl peptide derivatives by unlabeled N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys correlated closely with a dose-response curve for inhibition of binding of the same formyl peptide derivatives to the receptor. The nonformylated analog, Nle-Leu-Phe-Nle-Tyr-Lys, did not inhibit binding or covalent cross-linking.