mastoparan-b and Edema

Mastoparan B (MP-B) is a cationic tetradecapeptide isolated from the black-bellied hornet (Vespa basalis) venom. It has a primary structure (LKLKSIVSWAKKVL-CONH2) distinct from other vespine mastoparans. The peptide caused a dose-dependent swelling in rat hind paw and showed a potent hemolytic activity in guinea pig red blood cells. Studies on the structure activity relationship of the peptide showed that replacing lysine at position 2 (Lys2) by asparagine (Asn) in the MP-B sequence caused about 40% decrease in its edema-inducing activity at 50 micrograms/paw and 90% decrease in hemolytic activity at 30 microM of the peptide, while the same substitution at Lys4 did not cause a significant change in either activity. Replacing either Lys11 or Lys12 by leucine (Leu) caused little or no decrease in the edema-inducing and hemolytic activities. Decreases in both activities were observed when both Lys11 and Lys12 were replaced by Leu. On the other hand, replacing tryptophan at position 9 (Trp9) by tyrosine or phenylalanine in MP-B sequence almost abolished its hemolytic activity, while the edema-inducing activity was only partially inhibited. Circular dichroism spectra of the peptides measured in 20% trifluoro-ethanol revealed that substitution of Lys and Trp did not cause a significant change in the conformation of MP-B. it appears that Lys2 is crucial for both hemolytic and edema-inducing activities of MP-B, while Trp9 is of special importance to the hemolytic activity of MP-B. Lys11 and Lys12 in MP-B probably play a lesser role in both activities.

Topics: Amino Acid Sequence; Animals; Circular Dichroism; Dose-Response Relationship, Drug; Edema; Erythrocytes; Guinea Pigs; Hemolysis; Intercellular Signaling Peptides and Proteins; Lysine; Peptides; Rats; Rats, Wistar; Structure-Activity Relationship; Tryptamines; Wasp Venoms

Mastoparan B, a tetradecapeptide toxin (LKLKSIVSWAKKVL) isolated from the hornet (Vespa basalis) venom, was synthesized chemically. The physical and biological properties of both the native and synthetic peptides were studied and proved to be identical. Mastoparan B was found to have a potent antibacterial activity to both Gram negative and Gram positive bacteria.

Topics: Amino Acid Sequence; Animals; Chromatography, High Pressure Liquid; Circular Dichroism; Edema; Gram-Negative Bacteria; Gram-Positive Bacteria; Guinea Pigs; Intercellular Signaling Peptides and Proteins; Microbial Sensitivity Tests; Molecular Sequence Data; Peptides; Rats; Rats, Wistar; Spectrometry, Mass, Fast Atom Bombardment