A reverse search for antimicrobial peptides in Ciona intestinalis: identification of a gene family expressed in hemocytes and evaluation of activity.
In search of antimicrobial peptides in the tunicate Ciona intestinalis, we used the recently completed genome project and the substantial number of expressed sequence tag (EST) data available as a screening matrix. By this means, we identified a putative gene family that exhibits several structural features typical of antimicrobial peptides. We designed and synthesized a peptide corresponding to the core region of a member of this peptide family, which is predicted to adopt an amphipathic alpha-helical structure. The synthetic peptide exerted potent antimicrobial activity against a variety of bacteria and against the yeast Candida albicans but was not cytolytic for mammalian erythrocytes. Moreover, by employing a non-cell-permeable fluorescent dye it became evident that the peptide kills bacteria by permeabilizing their cytoplasmic membranes. Using the synthetic peptide as an antigen, we generated specific antibodies and localized the natural parent molecule to a compartment of a distinct hemocyte type, the univacuolar refractile granulocytes. As C. intestinalis apparently does not possess gene products that resemble well-known antimicrobial peptides of tunicates and of other animals, the aforementioned peptide family may represent a potent armamentarium of the hemocytes to combat microbial infection in sea squirts.
Department of Zoophysiology, Zoological Institute, University of Kiel, Olshausenstr. 40, 24098 Kiel, Germany.
Henning
H
Fedders
Matthias
M
Leippe
D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D001410:Bacillus megaterium / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D002938:Ciona intestinalis / Q000235:genetics* / Q000276:immunology; D019295:Computational Biology / Q000379:methods; D030541:Databases, Genetic; D004912:Erythrocytes / Q000187:drug effects; D020869:Gene Expression Profiling; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D006434:Hemocytes / Q000166:cytology / Q000378:metabolism*; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017403:In Situ Hybridization; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012756:Sheep
D023181:Antimicrobial Cationic Peptides