MOLECULAR-CLONING OF CDNAS ENCODING PRECURSORS OF FROG-SKIN ANTIMICROBIAL PEPTIDES FROM RANA-RUGOSA

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. Co mmun. 205, 948-954). Two complete cDNAs encoding gaegurins 4 and 5 wer e isolated from a library constructed with the frog skin mRNAs. Each c lone contained a single open reading frame that encodes a gaegurin pre cursor polypeptide. The deduced amino acid sequences revealed that the precursors have a unique tripartite structure: a putative signal sequ ence at the NH2-terminus followed by an acidic spacer region rich in g lutamic and aspartic acids, and a mature gaegurin peptide at the COOH- terminus. Similar modes of organization were also found in antimicrobi al 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 liv er and muscle.