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Staphylococcus aureus Tetrapeptide With High Chemotactic Potency and Efficacy for Human Leukocytes

A chemotactic tetrapeptide from culture fluids of Staphylococcus aureus was purified to homogeneity by reverse‐phase high‐pressure liquid chromatography. The peptide comprises equimolar methionine, leucine, isoleucine, and phenylalanine. It inhibited binding of fluoresceinated fMet‐Leu‐Phe‐Lys to human monocytes, which showed that it interacted with the formyl‐methionyl peptide receptor and suggested that it was a formyl‐methionyl peptide. Based on a comparison of dose‐response curves for inhibition of fluoresceinated fMet‐Leu‐Phe‐Lys binding, the relative affinity of the peptide for the receptor was comparable to that of fMet‐Leu‐Phe‐Lys. At optimal concentrations, chemotactic efficacy (percentage of monocytes migrating to the attractant) was 53 ± 4%, in contrast to 36 ± 3% for the reference attractant fMet‐Leu‐Phe. Since approximately 60% of human monocytes have formyl‐peptide receptors, the bacterial peptide is capable of attracting all receptor‐bearing monocytes.