Abstract
Mastoparan-B (MPB-NH2) is an antibacterial cationic tetradecapeptide, isolated from the venom of black-bellied hornet (Vespa basalis) with a primary structure (LKLKSIVSWAKKVL -CONH2) and amide C-terminus. It forms a random coil in aqueous solution and adopts an ampliphlic α-helical conformation in trifluoroethanol(TFE). A previous study showed that Alanine (Ala) in substitution for Trp9 cause a collapse of the helix. The aromatic ring of the tryptophan in MPB-NH2 is important in the helical stabilization. Recognizing this, we attempt to uncover how an aromatic residue affect the structure and the biological activity of MPB-NH2 and its analogous. In this study, we replaced Trp9 by phenylalanine and tyrosine in the primary structure of MPB-NH2. Results of CD and NMR indicated no significant change in the helical structure in 30% trifluoroethanol solution. However, the experiments of antibacterial activity showed that MPB-NH2 has stronger antibacterial activity than [Phe9]- MPB-NH2and [Tyr9]- MPB-NH2. It is likely that the indole ring of tryptophan residue is more effective for membrane perturbation than benzene ring of phenylalanine and the phenol of tyrosine. Also, a number of NOEs have been found between aromatic residue and other residues. Here, we proposed that some of these NOEs may imply the fundamental interaction for structure stabilization and activity.
Published Version
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