DOMAINS OF THE HUMAN NEUTROPHIL N-FORMYL PEPTIDE RECEPTOR INVOLVED ING-PROTEIN COUPLING - MAPPING WITH RECEPTOR-DERIVED PEPTIDES

Chemotactic signaling by the human neutrophil N-formyl peptide recepto r requires its association with heterotrimeric G protein. Synthetic pe ptides and a fusion protein derived from the intracellular regions of the receptor were used to identify sites which interact with G protein . A peptide derived from the second intracellular loop (C12R), and pep tides (F15R and S22L) and a fusion protein derived from the receptor's carboxyl terminus inhibited binding of anti-G(ialpha) antibody (R16,1 7) to G(ialpha) in a competitive enzyme-linked immunoassay, and antago nized pertussis-toxin catalyzed ADP-ribosylation of G(ialpha). C12R al so inhibited G protein-dependent, high affinity ligand binding to the receptor and physical coupling of receptor to G protein. In contrast, a peptide consisting of the entire third loop of the N-formyl peptide receptor was totally inactive in these assays. Collectively, these dat a suggest that the second intracellular loop and the carboxyl-terminal tail are important for effective N-formyl peptide receptor/G protein coupling, but that the third intracellular loop is less important in c oupling, unlike previous findings with other G protein-coupled recepto r systems. The chemoattractant receptor family may rely on different s tructural determinants to interact with GTP-binding proteins.