抄録
The major basic protein (MBP) plays an important role in the antiparasitic and antibacterial activities of eosinophils. In this study, to elucidate the mechanism of the action of MBP, the antibacterial peptides of MBP were isolated and their structures were analyzed.
The antibacterial activity of MBP was not affected by the pyridylethylation of the thiol groups of MBP, suggesting that the disulfide bonds were not necessary for the antibacterial activity of MBP.
By the chymotryptic digestion of pyridylethylated-MBP (PE-MBP), 14 peptides (peptide I-XIV) were obtained, and 6 peptides (peptide V, IX, X, XII, XIII and XIV) showed antibacterial activities. Amino acid sequences of the 4 peptides (peptide V, IX, X and XIII) which had high antibacterial activities, were analyzed. Interestingly, all the 4 peptides proved to have both the hydrophilic regions which were rich in basic amino acids and the hydrophobic regions.
By the chymotryptic digestion of peptide V and X, their antibacterial activities were significantly reduced. Amino acid sequence analyses of the digested peptides (peptide V and X) showed that the hydrophilic regions were separated from the hydrophobic regions after the digestion.
These observations suggest that both the hydrophilic and the hydrophobic regions are important for the expression of the antibacterial activity of MBP.
