cDNA cloning of halocidin and a new antimicrobial peptide derived from the N-terminus of Ci-META4

• Published in: Peptides (New York, N.Y. : 1980) Vol. 26; no. 12; pp. 2360 - 2367
• Main Authors: Jang, Woong Sik, Kim, Chong Han, Kang, Min Sook, Chae, Hee Jeong, Son, Seok Min, Seo, Sook Jae, Lee, In Hee
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.12.2005; Elsevier Science
• Subjects: Amino Acid Sequence; Animals; Anti-Infective Agents - chemistry; Anti-Infective Agents - pharmacology; Antimicrobial peptide; Bacteria - growth & development; Base Sequence; Biological and medical sciences; cDNA cloning; Ci-META4; Cloning, Molecular; Dose-Response Relationship, Drug; Erythrocytes - drug effects; Fundamental and applied biological sciences. Psychology; Halocidin; Halocynthia aurantium; Hemolysis - drug effects; Humans; Microbial Sensitivity Tests; Molecular Sequence Data; Peptides - chemistry; Peptides - genetics; Peptides - pharmacology; Tunicate; Urochordata - chemistry; Urochordata - genetics; Vertebrates: endocrinology; Halocynthia aurantium; cDNA cloning; Tunicate; Ci-META4; Halocidin; Antimicrobial peptide; Peptides; Antibacterial agent; Antimicrobial agent
• ISSN: 0196-9781; 1873-5169
• DOI: 10.1016/j.peptides.2005.05.004

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.