Possible Mechanisms of Bactericidal and Tumoricidal Effects Induced by Sushi 3 Derived Peptides

• Main Authors: Yi-Jing Lian, 連苡淨
• Other Authors: Je-Wen Liou
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/52595159948121325318

碩士 === 慈濟大學 === 微生物學免疫學暨生物化學碩士班 === 101 === Most antimicrobial peptides exhibiting bactericidal functions are related to the characteristics of the surfaces of the bacterial cells which consist of mostly negatively charged phosphatidylglycerol, peptidoglycan and lipopolysaccharide. Most of the antimicrobial peptides are positively charged and are selectively interact with the bacterial cell surfaces and cause disruptions of the cell membranes. As shown in recent studies, many positively charged antimicrobial peptides also have anticancer activity. This study intended to design antimicrobial peptides with antimicrobial and anticancer activities and tried to find out if the production of hydroxyl radical during the treatments of peptides on bacteria plays a role in the killing mechanism of these peptides Horseshoe Crab Sushi 3 peptide was used of as the template for peptide design. A sections of 20 amino acids were taken from the middle part of the original 34 amino acid Sushi 3 peptides (the 20 amino acid peptide sequence is called S3) and the mutations are made in the sequence to yield the peptides with different -helix contents based on bioinformatic secondary structure predictions. A series of sequences are selected for peptide synthesis with a solid phase approach. The synthesized peptides were purified with high-performance liquid chromatography. The amino acids sequences were checked by mass spectrometry. And the hydroxyl radical production during the treatments was examined by flow cytometry with hydroxyl radical specific dye to find out if the hydroxyl radical production is indeed related to the structure of the peptides. The apoptosis of the cancer cells was studied by cell viability assay and western blotting analysis. According to our results, bacterial survival rate of E. coli and MRSA treated with S3 peptide and S3 mutants showed that these peptides were not very powerful for bacteria killing, although they are still effective to bacteria. S3 peptide and S3 mutants did not show hemolytic activity to the erythrocyte. In the flow cytometry study, only the highly helical structured S3-14 induced significant hydroxyl radical production in E. coli during the treatments. In the anticancer investigations, we found that S3 wild type and S3-14 might be able to induce apoptosis in HeLa cancer cells.