title: Molecular characterization of a novel antimicrobial peptide from Mytilus coruscus.
abstract: Antimicrobial peptides (AMPs) are components of the innate immune responses that form the first line of host defense against pathogens. Marine mussels can produce a surprising abundance of cysteine-rich AMPs pertaining to the defensin, myticin, mytilin and mytimycin families, particularly in the circulating hemocytes. In the current study, we purified and characterized a novel cysteine-rich peptide with remarkable antibacterial activity from Mytilus coruscus and designated with myticusin-1, a 104-amino acid long polypeptide including 10 cysteine residues forming an unusual cysteine pattern. Antimicrobial assays demonstrated that myticusin-1 exhibited stronger anti-microbial properties against Gram-positive bacteria more than Gram-negative bacteria and fungus. Furthermore, myticusin-1 caused significant morphological alterations in both Sarcina luteus and Escherichia coli as shown by transmission electron microscopy (TEM). The cDNA of myticusin-1 was cloned and sequenced from the hemocytes cDNA library of M. coruscus. The mRNA transcripts of myticusin-1 are mainly detected in hemocyte, which indicates that myticusin-1 are specifically synthesized and stored in circulating hemocytes. The expression level of myticusin-1 in hemocytes was up-regulated and reached the highest level at 36 h after S. luteus challenge, which was 20-fold increase compared to that of the control group. These results indicated that myticusin-1 was involved in the host immune response against bacterial infection and might contribute to the clearance of invading bacteria.
authors.affiliation: Key Laboratory for Marine Living Resources and Molecular Engineering, College of Marine Science, Zhejiang Ocean University, Zhoushan 316000, Zhejiang Province, PR China. liaozhi@zjou.edu.cn
authors.forename: Zhi
authors.initials: Z
authors.lastname: Liao
authors.forename: Xin-chao
authors.initials: XC
authors.lastname: Wang
authors.forename: Hui-hui
authors.initials: HH
authors.lastname: Liu
authors.forename: Mei-hua
authors.initials: MH
authors.lastname: Fan
authors.forename: Jing-jing
authors.initials: JJ
authors.lastname: Sun
authors.forename: Wang
authors.initials: W
authors.lastname: Shen
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology*; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000648:ultrastructure; D006434:Hemocytes / Q000378:metabolism; D007113:Immunity, Innate / Q000276:immunology*; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D049878:Mytilus / Q000737:chemistry* / Q000276:immunology; D060888:Real-Time Polymerase Chain Reaction; D012505:Sarcina / Q000187:drug effects / Q000648:ultrastructure; D017422:Sequence Analysis, DNA; D018675:Toxicity Tests
chemical_list: D023181:Antimicrobial Cationic Peptides; D017931:DNA Primers; D018076:DNA, Complementary