Molecular cloning of cDNAs encoding precursors of frog skin antimicrobial peptides from Rana rugosa

Abstract Gaegurins, a family of peptide antibiotics with sizes ranging from 24 to 37 amino acids, have recently been purified from Rana rugosa skin (Park, J.M., Jung, J.-E. and Lee, B.J. (1994) Biochem. Biophys. Res. Commun. 205, 948–954). Two complete cDNAs encoding gaegurins 4 and 5 were isolated from a library constructed with the frog skin mRNAs. Each clone contained a single open reading frame that encodes a gaegurin precursor polypeptide. The deduced amino acid sequences revealed that the precursors have a unique tripartite structure: a putative signal sequence at the NH 2 -terminus followed by an acidic spacer region rich in glutamic and aspartic acids, and a mature gaegurin peptide at the COOH-terminus. Similar modes of organization were also found in antimicrobial or opioid peptide precursors of other frog species, although their mature peptides show little sequence homology. The family of peptides with this characteristic now expands. Northern analysis revealed that gaegurins are extensively expressed in the skin tissue, but not in liver and muscle.