2Hematology and Oncology Research Center, Shahid Sadoughi University of Medical Sciences and Health Services, Yazd, Iran
3Department of Biotechnology, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, Iran
5Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran
6Department of Biology, Faculty of Sciences, Iranshahr Branch, Payam Noor University of Sistan and Baluchestan, Iranshahr, Iran
7Biotechnology Department, Agriculture Faculty, Ferdowsi University of Mashhad, Mashhad, Iran
* To whom correspondence should be addressed.
Received September 19, 2014; Revision received November 26, 2014
Antimicrobial peptides are members of the immune system that protect the host from infection. In this study, a potent and structurally novel antimicrobial peptide was isolated and characterized from praying mantis Sphodromantis viridis. This 14-amino acid peptide was purified by RP-HPLC. Tandem mass spectrometry was used for sequencing this peptide, and the results showed that the peptide belongs to the Mastoparan family. The peptide was named Mastoparan-S. Mastoparan-S demonstrated that it has antimicrobial activities against a broad spectrum of microorganisms (Gram-positive and Gram-negative bacteria and fungi), and it was found to be more potent than common antibiotics such as kanamycin. Mastoparan-S showed higher antimicrobial activity against Gram-negative bacteria compared to Gram-positive ones and fungi. The minimum inhibitory concentration (MIC) values of Mastoparan-S are 15.1-28.3 µg/ml for bacterial and 19.3-24.6 µg/ml for fungal pathogens. In addition, this newly described peptide showed low hemolytic activity against human red blood cells. The in vitro cytotoxicity of Mastoparan-S was also evaluated on monolayer of normal human cells (HeLa) by MTT assay, and the results illustrated that Mastoparan-S had significant cytotoxicity at concentrations higher than 40 µg/ml and had no any cytotoxicity at the MIC (≤30 µg/ml). The findings of the present study reveal that this newly described peptide can be introduced as an appropriate candidate for treatment of topical infection.
KEY WORDS: antimicrobial peptides, cytotoxicity, Sphodromantis viridis, immune system, hemolytic activity