The Structure Molecular Designation And Antimicrobial Activity Of Antibacterial Peptide From Mytilus Coruscus

Antibacterial peptide is a class of small molecular peptides produced by the organism when it's resisting pathogenic microbes. It has the advantages of high efficient sterilization and low risk of drug resistance, so it has the broad prospect in developing new organism antibiotics. Now the research on marine antibacterial peptides becomes one of the hot topics.We studied the Mytilin-1 derived from serum of Mytilus coruscus and simulated its spatial structure for studying the relationship between spatial structure and antimicrobial activity and providing new ideas of manual designation and modification of Mytilin. For verification of the functional fragment of Mytilin-1, we synthesized two decapeptides corresponding to the main mimic structures connected theα-fold andβ-hairpin of mytilin-1 from Mytilus coruscus and evaluated their activities. The two decapeptides, which named MDP-1(Mytilin derived peptide-1) and MDP-2, were re-designed and synthesized by solid-phase peptide synthesis methods.The antibacterial test of MDP-1 and MDP-2 shows that MDP-2 has stronger activity than MDP-1 despite the fact that both peptides can inhibit the growth of Gram-positive, Gram-negative bacteria and fungi. MDP-2 possesses the obvious inhibition to marine vibrio and pathogen. MDP-1 and MDP-2 have strong thermal stability, and their antibacterial activities didn't drop obviously after culturing in the human plasm for 24h, 37℃.For better understanding the relationship between spatial structure and function of MDP-1 and MDP-2, we analysis their spatial structure by 1H NMR。The result indicates that compared with structure of Mytilin-1, MDP-1 and MDP-2 have no regular structures ofβ-hairpin in loop area, and they have irregular loop structures instead. The amino acid sequences of MDP-1 and MDP-2 are opposite, which makes the trends of main chains are different. Meanwhile, the position of residues in the side chains are different, especially the position of Arg. The two Args of MDP-1 distribute on opposite side of the loop, but the two Args of MDP-2 distribute on same side, which help to make the positive charge more concentrate. According to the previous research, the two Arg are considered the functional part of antimicrobial activity. So the distribution difference of the two Arg may determine the intensity of antimicrobial activity.The results lay a foundation for further research on the antibacterial mechanism of Mytilin and for further exploitation of antibacterial peptides with lower molecular mass and more stable structure.