The Study Of Membrane-active Action Mode Of Polybia-CP

In1940s, with the discovery of the antibiotics, there is a revolution in the medicine. Since then, people could cure a lot of infection diseases. However, as the extensive use of antibiotics in medicine, food and farming industry, the frequent emergency of resistant bacteria has brought great threat to life. The defeat between antibiotic and infection disease become more and more serious. All of this needs us to development new drugs with high activity, low mammalian toxicity and new antimicrobial activity exhibition modes. As their name implies, antimicrobial peptides (AMPs) are small molecules (usually from 2000 to 7000) with antimicrobial activity, and have 20 to 60 amino acids. Antimicrobial peptides (AMPs) constitute the first line of defense against invading microorganism. AMPs possess broad antimicrobial activity against bacteria, fungi, virus and tumor cells. The antimicrobial activity exhibition mode of AMPs has been associated with destruction of bacteria membrane and intracellular degradation events. It is now widely recognized that antimicrobial peptides (AMPs) could play a promising role in fighting the multi-drug resistant bacteria. Antimicrobial peptide polybia-CP was purified from the venom of the social wasp Polybia paulista. Its primary sequence was ILGTILGLLKSL-NH2(1239.73Da). In this study, we synthesized polybia-CP and use Electro Spray Ionization-Mass Spectroscopy to confirm its molecular weight. Reverse phase high-performance liquid chromatography was used to get purifier peptides. Because, there is similarities between the membrane of bacteria and tumor cells. At first, we studied the cytotoxicity and the exhibition mode of polybia-CP to tumor cells. In order to further characterize the mechanism of peptide-lipid bilayer of cell membranes, molecular dynamics (MD) simulation was employed to describe the spatial organization and temporal dynamics of the system. Our results revealed that polybia-CP has cytotoxicity to tumour cells and its site of action is the membrane of the tumor cells. Then, we studied the activity of polybia-CP to the bacteria including Gram-positive and Gram-negative bacteria. Furthermore, we use some methods to study the mechanism of polybia-CP to the bacteria. For example, in order to understand the influence of AMPs on the integrity of bacteria membrane, lipid membrane models, such as LUVs (EYPC/EYPG 7:3), was used in research work to exclude the influence of proteins and sugars. Our results found that polybia-CP has potent antimicrobial activity to both Gram-positive and Gram-negative bacteria. Both the real bacteria membrane and in vitro model membrane showed that polybia-CP is membrane active and its action target is the membrane of bacteria. It is difficult for bacteria to develop resistance to polybia-CP, which may offer a new strategy to defend the resistant bacteria in medicine, food and farming industry.So, our study will be useful for the development of new drugs.