Antimicrobial activity of synthetic all-d mastoparan M

Abstract Mastoparan M, a tetradecapeptide toxin (INKAIAALAKKLL-NH2) from hornet venom and its d-form mastoparan M were synthesized chemically. All d- and l-mastoparan M forms were found to adopt 28% α-helical structures in a 30% trifluroethanol solution as shown by the circular dichroism spectrum. All-d mastoparan M caused 3 H-thymidine release from labeled bacterial cells after incubation for 1 h and complete cell lysis by 4 h. Both l- and d-mastoparan M showed strong activity against Gram-positive and Gram-negative bacteria. All-d mastoparan M showed 2-fold higher antibacterial activity than l-mastoparan M. The effects of all-d mastoparan M on the surface morphology of Staphylococcus aureus (ATCC29213) and Escherichia coli (ATCC25922) were studied by scanning-beam electron microscopy. Blast-like bleb extrusions on the surface of some S. aureus and swellings on the end of E. coli were seen after culture with all-d mastoparan M. These findings indicated the all-d mastoparan M could kill bacteria by disrupting cells.