The formyl peptide receptor (FPR) is activated by small peptides derived from bacterial and mitochondrial proteins, often with a formylated N terminal methionine and usually a hydrophobic amino acid at the carboxy terminal end. Formyl-MetLeuPhe is the most commonly used peptide ligand, leading to a widespread use of the name fMetLeuPhe receptor.
Formyl peptides are produced by the degradation of either bacterial or host cells. They have a wide range of biological activities including the stimulation of chemotaxis and secretory activities of leukocytes, particularly neutrophils and monocytes. Formyl peptide receptors are involved in mediating immune cell responses to infection.