Peptide-based analysis of amino acid sequences important to the biologicalactivity of eosinophil granule major basic protein

Synthetic peptides corresponding to amino acid sequences in eosinophil gran ule major basic protein (MBP) were evaluated for cytotoxic activity toward K562 cells and for ability to stimulate basophil mediator release. Results obtained using 14 peptides spanning the 117-amino acid sequence of MBP in o verlapping fashion indicated that the activities mapped to peptide sequence s near the amino and carboxy termini of MBP. The activity of these regions was confirmed using two peptides corresponding to MBP residues 18-45 and 89 -117. A 20-h incubation with 5 muM MBP peptide 18-45 or peptide 89-117 caus ed approximately the same levels ( > 60%) of cytotoxicity in K562 cells as 5 muM MBP. Similarly, a 30-min incubation with peptides 18-44 and 89-117 st imulated basophil histamine release in a concentration-dependent manner ove r the range of 5-20 muM, The level of release stimulated by 20 muM peptide 89-117 approached that stimulated by 2 muM MBP. A 20 muM concentration of p eptide 89-117 also stimulated leukotriene C4 (LTC4) production by the basop hils. Neither peptide 18-45 nor peptide 89-117 was cytotoxic for basophils under the experimental conditions For histamine and LTC4 release, as determ ined by Cr-51 release. These results indicate that two MBP peptide sequence s. including one (89-117) that contains a unique carbohydrate-binding regio n, share the biologic activities of MBP. (C) 2001 Elsevier Science B.V. All rights reserved.