cDNA cloning of halocidin and a new antimicrobial peptide derived from the N-terminus of Ci-META4 |
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Authors: | Jang Woong Sik Kim Chong Han Kang Min Sook Chae Hee Jeong Son Seok Min Seo Sook Jae Lee In Hee |
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Affiliation: | aDepartment of Bio-Technology, Hoseo University, Asan City, Chungnam-Do 336-795, South Korea bDepartment of Food Biotechnology, Hoseo University, Asan City, Chungnam-Do 336-795, South Korea cDivision of Life Science, College of Natural Sciences, Gyeongsang National University, Chinju, South Korea |
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Abstract: | Halocidin is an antimicrobial peptide, which is isolated from hemocytes from the tunicate, Halocynthia aurantium. In this study, we cloned the full-length cDNA of halocidin from pharyngeal tissue, using a combination of RT-PCR and 5′-RACE-PCR. The observed cDNA structure indicated that halocidin is synthesized as a 10.37 kDa prepropeptide. Based on the cDNA structure and the known amino acid sequence of the mature peptide, it was concluded that the precursor of halocidin contains a 21-residue signal peptide, followed by the 18 residues of the mature peptide, and a 56-residue anionic C-terminal extension, which is removed later on in the process. The signal sequence of halocidin exhibited a high degree of similarity with the corresponding portion of the Ci-META4 protein, which had been previously discovered in the coelomic cells of another tunicate, Ciona intestinalis, and is considered to play a role in metamorphosis. However, in several respects, the cDNA structure of Ci-META4 suggested that it might constitute a precursor for an antimicrobial peptide. Thus, we prepared a synthetic peptide, which was comprised of 19 N-terminal amino acid residues in the predicted mature region of Ci-META4, and tested it with regard to its antimicrobial activity. As a result, we confirmed that the synthetic peptide exhibited potent antimicrobial activity against Gram (+) and (−) bacteria, while evidencing no hemolytic activity toward human erythrocytes. |
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Keywords: | Halocidin cDNA cloning Antimicrobial peptide Halocynthia aurantium Tunicate Ci-META4 |
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